In 1968, Keaton became a member of the “Tribe” and understudy to Sheila in the original Broadway production of Hair. She gained some notoriety for her refusal to disrobe at the end of Act I when the cast performs nude, even though nudity in the production was optional for actors (Those who performed nude received a $50 bonus). After acting in Hair for nine months, she auditioned for a part in Woody Allen’s production of Play It Again, Sam. After nearly being passed over for being too tall (at 5 ft 8 in (173 cm), she is 2 inches (5 cm) taller than Allen), she won the part.

In addition to acting, Keaton has said she “had a lifelong ambition to be a singer.” She had a brief, unrealized career as a recording artist in the 1970s. Her first record was an original cast recording of Hair, in 1971. In 1977 she began recording tracks for a solo album, but the finished record never materialized.

Keaton has had several romantic associations with noted entertainment industry personalities, starting with her audition for the 1969 Broadway production of Play It Again, Sam, directed by Woody Allen. Their relationship became romantic after they had dinner after a late-night rehearsal. It was her sense of humor that attracted Allen. They briefly lived together during the production, but by the time of the film release of the same name in 1972, their living arrangements became informal. They worked together on eight films between 1971 and 1993, and Keaton has said that Allen remains one of her closest friends.

In 1977 Keaton won the Academy Award for Best Actress in Allen’s romantic comedy Annie Hall, one of her most famous roles. Annie Hall, written by Allen and Marshall Brickman and directed by Allen, was believed by many to be an autobiographical exploration of his relationship with Keaton. Allen based the character of Annie Hall loosely on Keaton (“Annie” is a nickname of hers, and “Hall” is her original surname). Many of Keaton’s mannerisms and her self-deprecating sense of humor were added into the role by Allen. (Director Nancy Meyers has claimed “Diane’s the most self-deprecating person alive.”) Keaton has also said that Allen wrote the character as an “idealized version” of herself. The two starred as a frequently on-again, off-again couple living in New York City. Her acting was later summed up by CNN as “awkward, self-deprecating, speaking in endearing little whirlwinds of semi-logic”, and by Allen as a “nervous breakdown in slow motion.” The film was both a major financial and critical success, and won the Academy Award for Best Picture. Of Keaton’s performance, feminist film critic Molly Haskell wrote, “Keaton took me by surprise in Annie Hall. Here she blossomed into something more than just another kooky dame—she put the finishing touches on a type, the anti-goddess, the golden shiksa from the provinces who looks cool and together, who looks as if she must have a date on Saturday night, but has only to open her mouth or gulp or dart spastically sideways to reveal herself as the insecure bungler she is, as complete a social disaster in her own way as Allen’s horny West Side intellectual is in his.” In 2006 Premiere magazine ranked Keaton in Annie Hall 60th on its list of the “100 Greatest Performances of All Time”, and noted:

With Manhattan (1979), Keaton and Woody Allen ended their long working relationship; it was their last major collaboration until 1993. In 1978 she became romantically involved with Warren Beatty, and two years later he cast her opposite him in the epic historical drama Reds. In the film she played Louise Bryant, a journalist and feminist, who flees her husband to work with radical journalist John Reed (Beatty) and later enters Russia to find him as he chronicles the Russian Civil War. Beatty cast Keaton after seeing her in Annie Hall, as he wanted to bring her natural nervousness and insecure attitude to the role. The production of Reds was delayed several times following its conception in 1977, and Keaton almost left the project when she believed it would never be produced. Filming finally began two years later. In a 2006 Vanity Fair story, Keaton described her role as “the everyman of that piece, as someone who wanted to be extraordinary but was probably more ordinary … I knew what it felt like to be extremely insecure.” Assistant director Simon Relph later stated that Louise Bryant was one of Keaton’s most difficult roles, and that “[she] almost got broken.” Reds opened to critical acclaim, and Keaton’s performance was particularly praised. The New York Times wrote that Keaton was “nothing less than splendid as Louise Bryant – beautiful, selfish, funny and driven. It’s the best work she has done to date.” Roger Ebert called Keaton “a particular surprise. I had somehow gotten into the habit of expecting her to be a touchy New Yorker, sweet, scared, and intellectual. Here, she is just what she needs to be: plucky, healthy, exasperated, loyal, and funny.” Keaton received her second Academy Award nomination for her performance.

Keaton was already dating Warren Beatty in 1979 when they co-starred in the film Reds. Beatty was a regular subject in tabloid magazines and media coverage, and Keaton became included, much to her bewilderment. In 1985 Vanity Fair called her “the most reclusive star since Garbo.” This relationship ended shortly after Reds wrapped. Troubles with the production are thought to have strained the relationship, including numerous financial and scheduling problems. Keaton remains friends with Beatty.

1984 brought The Little Drummer Girl, Keaton’s first excursion into the thriller and action genre. The Little Drummer Girl was both a financial and critical failure, with critics claiming that Keaton was miscast for the genre, such as one review from The New Republic claiming that “the title role, the pivotal role, is played by Diane Keaton, and around her the picture collapses in tatters. She is so feeble, so inappropriate.” But the same year she received positive reviews for her performance in Mrs. Soffel, a film based on the true story of a repressed prison warden’s wife who falls in love with a convicted murderer and arranges for his escape. Two years later she starred with Jessica Lange and Sissy Spacek in Crimes of the Heart, adapted from Beth Henley’s Pulitzer Prize-winning play into a moderately successful screen comedy. Keaton’s performance was well received by critics, and Rita Kempley of The Washington Post wrote, “As the frumpy Lenny, Keaton eases smoothly from New York neurotic to southern eccentric, a reluctant wallflower stymied by, of all things, her shriveled ovary.”

In 1987 Keaton starred in Baby Boom, her first of four collaborations with writer-producer Nancy Meyers. She played a Manhattan career woman who is suddenly forced to care for a toddler. A modest box-office success, Keaton’s performance was singled out by Kael, who described it as “a glorious comedy performance that rides over many of the inanities in this picture. Keaton is smashing: the Tiger Lady’s having all this drive is played for farce and Keaton keeps you alert to every shade of pride and panic the character feels. She’s an ultra-feminine executive, a wide-eyed charmer, with a breathless ditziness that may remind you of Jean Arthur in The More The Merrier.” That same year Keaton made a cameo in Allen’s film Radio Days as a nightclub singer. 1988’s The Good Mother was a financial disappointment (according to Keaton, the film was “a Big Failure. Like, BIG failure”), and some critics panned her performance; according to The Washington Post, “her acting degenerates into hype—as if she’s trying to sell an idea she can’t fully believe in.”

In 1987 Keaton directed and edited her first feature film, Heaven, a documentary about the possibility of an afterlife. It met with mixed critical reaction, with The New York Times likening it to “a conceit imposed on its subjects.” Over the next four years Keaton directed music videos for artists such as Belinda Carlisle, including the video for Carlisle’s chart-topping hit “Heaven Is a Place on Earth,” two television films starring Patricia Arquette, and episodes of the series China Beach and Twin Peaks.

Keaton has continued to pursue her interest in photography. In 1987 she told Vanity Fair, “I have amassed a huge library of images—kissing scenes from movies, pictures I like. Visual things are really key for me.” She has published several more collections of her own photographs and served as an editor of collections of vintage photography. Works she has edited in the last decade include a book of photographs by paparazzo Ron Galella; an anthology of reproductions of clown paintings; and a collection of photos of California’s Spanish-Colonial-style houses.

Keaton began the decade with The Lemon Sisters, a poorly received comedy/drama that she starred in and produced, which was shelved for a year after its completion. In 1991 she starred with Steve Martin in the family comedy Father of the Bride. She was almost not cast in the film, as The Good Mother’s commercial failure had strained her relationship with Walt Disney Pictures, the studio of both films. Father of the Bride was Keaton’s first major hit after four years of commercial disappointments. She reprised her role four years later in the sequel, as a woman who becomes pregnant in middle age at the same time as her daughter. A San Francisco Examiner review of the film was one of many in which Keaton was once again compared to Katharine Hepburn: “No longer relying on that stuttering uncertainty that seeped into all her characterizations of the 1970s, she has somehow become Katharine Hepburn with a deep maternal instinct, that is, she is a fine and intelligent actress who doesn’t need to be tough and edgy in order to prove her feminism.”

Keaton reprised her role of Kay Adams in 1990’s The Godfather Part III, set 20 years after the end of The Godfather, Part II. Keaton’s character was now Michael Corleone’s estranged ex-wife. Criticism of the film and Keaton again centered on her character’s unimportance in the film. The Washington Post wrote, “Even though she is authoritative in the role, Keaton suffers tremendously from having no real function except to nag Michael for his past sins.” In 1993 Keaton starred in Manhattan Murder Mystery, her first major film role in a Woody Allen film since 1979. Her part was originally intended for Mia Farrow, but Farrow dropped out of the project after breaking up with Allen. Todd McCarthy of Variety commended her performance, writing that she “nicely handles her sometimes buffoonish central comedic role”. David Ansen of Newsweek wrote, “On screen, Keaton and Allen have always been made for each other: they still strike wonderfully ditsy sparks”. For her performance, Keaton was nominated for a Golden Globe Award for Best Actress – Motion Picture Comedy or Musical.

In 1995 Keaton directed Unstrung Heroes, her first theatrically released narrative film. The movie, adapted from Franz Lidz’s memoir, starred Nathan Watt as a boy in the 1960s whose mother (Andie MacDowell) becomes ill with cancer. As her sickness advances and his inventor father (John Turturro) grows increasingly distant, the boy is sent to live with his two eccentric uncles (Maury Chaykin and Michael Richards). Keaton switched the story’s setting from the New York of Lidz’s book to the Southern California of her own childhood, and the four mad uncles were reduced to a whimsical odd couple. In an essay for The New York Times, Lidz said that the cinematic Selma had died not of cancer, but of “Old Movie Disease”. “Someday somebody may find a cure for cancer, but the terminal sappiness of cancer movies is probably beyond remedy.” Unstrung Heroes played in a relatively limited release and made little impression at the box office, but the film and its direction were generally well-received critically.

Also in 1996 Keaton starred as Bessie, a woman with leukemia, in Marvin’s Room, an adaptation of the play by Scott McPherson. Meryl Streep played her estranged sister, Lee, and had also initially been considered for the role of Bessie. The film also starred Leonardo DiCaprio as Lee’s rebellious son. Roger Ebert wrote, “Streep and Keaton, in their different styles, find ways to make Lee and Bessie into much more than the expression of their problems.” Keaton earned a third Academy Award nomination for the film, which was critically acclaimed. She said the role’s biggest challenge was understanding the mentality of a person with a terminal illness. Keaton next starred in The Only Thrill (1997) opposite her Baby Boom co-star Sam Shephard, and had a supporting role in The Other Sister (1999).

Keaton’s first film of 2000 was Hanging Up, with Meg Ryan and Lisa Kudrow. She directed the film, despite claiming in a 1996 interview that she would never direct herself in a film, saying “as a director, you automatically have different goals. I can’t think about directing when I’m acting.” A drama about three sisters coping with the senility and eventual death of their elderly father (Walter Matthau), Hanging Up rated poorly with critics and grossed a modest US$36 million at the North American box office.

Keaton’s most successful film of the decade was the 1996 comedy The First Wives Club. She starred with Goldie Hawn and Bette Midler as a trio of “first wives”: middle-aged women who had been divorced by their husbands in favor of younger women. Keaton claimed that making the film “saved [her] life.” The film was a major success, grossing US$105 million at the North American box office, and it developed a cult following among middle-aged women. Its reviews were generally positive for Keaton and her co-stars, and The San Francisco Chronicle called her “probably [one of] the best comic film actresses alive.” In 1997 Keaton, Hawn and Midler received the Women in Film Crystal Award, which honors “outstanding women who, through their endurance and the excellence of their work, have helped to expand the role of women within the entertainment industry.”

In 1999 Keaton narrated the one-hour public-radio documentary “If I Get Out Alive”, the first to focus on the conditions and brutality young people face in the adult correctional system. The program, produced by Lichtenstein Creative Media, aired on public radio stations across the country, and was honored with a First Place National Headliner Award and a Casey Medal for Meritorious Journalism.

In 2001 Keaton co-starred with Warren Beatty in Town & Country, a critical and financial fiasco. Budgeted at an estimated US$90 million, the film opened to little notice and grossed only US$7 million in its North American theatrical run. Peter Travers of Rolling Stone wrote that Town & Country was “less deserving of a review than it is an obituary….The corpse took with it the reputations of its starry cast, including Warren Beatty and Diane Keaton.” In 2001 and 2002 Keaton starred in four low-budget television films. She played a fanatical nun in the religious drama Sister Mary Explains It All, an impoverished mother in the drama On Thin Ice, and a bookkeeper in the mob comedy Plan B. In Crossed Over, she played Beverly Lowry, a woman who forms an unusual friendship with the only woman executed while on death row in Texas, Karla Faye Tucker.

In July 2001, Keaton said of being older and unmarried, “I don’t think that because I’m not married it’s made my life any less. That old maid myth is garbage.” Keaton has two adopted children, daughter Dexter (adopted 1996) and son Duke (2001). Her father’s death made mortality more apparent to her, and she decided to become a mother at age 50. She later said of having children, “Motherhood has completely changed me. It’s just about the most completely humbling experience that I’ve ever had.”

Keaton has served as a producer on films and television series. She produced the Fox series Pasadena, which was canceled after airing only four episodes in 2001 but completed its run on cable in 2005. In 2003 she produced the Gus Van Sant drama Elephant, about a school shooting. Of why she produced the film, she said, “It really makes me think about my responsibilities as an adult to try and understand what’s going on with young people.”

Keaton met with more success in the medium of still photography. Like her character in Annie Hall, Keaton had long relished photography as a favorite hobby, an interest she picked up as a teenager from her mother. While traveling in the late 1970s, she began exploring her avocation more seriously. “Rolling Stone had asked me to take photographs for them, and I thought, ‘Wait a minute, what I’m really interested in is these lobbies, and these strange ballrooms in these old hotels.’ So I began shooting them”, she recalled in 2003. “These places were deserted, and I could just sneak in anytime and nobody cared. It was so easy and I could do it myself. It was an adventure for me.” Reservations, her collection of photos of hotel interiors, was published in book form in 1980.

Keaton has also established herself as a real estate developer. She has resold several mansions in Southern California after renovating and redesigning them. One of her clients was Madonna, who purchased a US$6.5 million Beverly Hills mansion from Keaton in 2003. She received the Film Society of Lincoln Center’s Gala Tribute in 2007.

Keaton opposes plastic surgery. She told More magazine in 2004, “I’m stuck in this idea that I need to be authentic … My face needs to look the way I feel.”

Since 2005 Keaton has been a contributing blogger at The Huffington Post. Since 2006 she has been the face of L’Oréal.

In 2007 Keaton starred in both Because I Said So and Mama’s Boy. In the romantic comedy Because I Said So, directed by Michael Lehmann, Keaton played a long-divorced mother of three daughters, determined to pair off her only single daughter, Milly (Mandy Moore). Also starring Stephen Collins and Gabriel Macht, the project opened to overwhelmingly negative reviews, with Wesley Morris of The Boston Globe calling it “a sloppily made bowl of reheated chick-flick cliches”, and was ranked among the worst-reviewed films of the year. The following year Keaton received her first and only Golden Raspberry Award nomination to date for the film. In Mama’s Boy, director Tim Hamilton’s feature film debut, Keaton starred as the mother of a self-absorbed 29-year-old (Jon Heder) whose world turns upside down when his widowed mother starts dating and considers booting him out of the house. Distributed for a limited release to certain parts of the United States only, the independent comedy garnered largely negative reviews.

In 2008 Keaton starred alongside Dax Shepard and Liv Tyler in Vince Di Meglio’s dramedy Smother, playing the overbearing mother of an unemployed therapist, who decides to move in with him and his girlfriend after breaking up with her husband (Ken Howard). As with Mama’s Boy, the film received a limited release only, resulting in a gross of US$1.8 million worldwide. Critical reaction to the film was generally unfavorable, and once again Keaton was dismissed for her role choices, with Sandra Hall of the New York Post writing, “Diane’s career is dyin’ […] this time, sadly, she’s gone too far. She’s turned herself into a mother-in-law joke.” Also in 2008 Keaton appeared alongside Katie Holmes and Queen Latifah in the crime-comedy film Mad Money, directed by Callie Khouri. Based on the British television drama Hot Money (2001), the film revolves around three female employees of the Federal Reserve who scheme to steal money that is about to be destroyed. As with Keaton’s previous projects, the film bombed at the box offices with a gross total of US$26.4 million, and was universally panned, ranking third in the New York Post’s Top 10 Worst Movies of 2008.

In 2010 Keaton starred alongside Rachel McAdams and Harrison Ford in Roger Michell’s comedy Morning Glory, playing the veteran TV host of a fictional morning talk show that desperately needs to boost its lagging ratings. Portraying a narcissistic character who will do anything to please the audience, Keaton described her role as “the kind of woman you love to hate.” Inspired by Neil Simon’s 1972 Broadway play The Sunshine Boys, the film was a moderate success at the box office, taking a worldwide total of almost US$59 million. Some critics felt that Keaton was underused in the film, but she was generally praised for her performance, with James Berardinelli of ReelViews writing, “Diane Keaton is so good at her part that one can see her sliding effortlessly into an anchor’s chair on a real morning show.”

In fall 2010 Keaton joined the production of the comedy drama Darling Companion by Lawrence Kasdan, which was released in 2012. Co-starring Kevin Kline and Dianne Wiest and set in Telluride, Colorado, the film follows a woman, played by Keaton, whose husband loses her much-beloved dog at a wedding held at their vacation home in the Rocky Mountains, resulting in a search party to find the pet. Kasdan’s first film in nine years, the film bombed at the US box office, where it scored about US$790,000 throughout its entire theatrical run. Critics dismissed the film as “an overwritten, underplotted vanity project” but applauded Keaton’s performance. Ty Burr of The Boston Globe wrote that the film “would be instantly forgettable if not for Keaton, who imbues [her role] with a sorrow, warmth, wisdom, and rage that feel earned […] Her performance here is an extension of worn, resilient grace.”

Also in 2011 Keaton began production on Justin Zackham’s 2013 ensemble comedy The Big Wedding, a remake of the 2006 French film Mon frère se marie in which she, along with Robert De Niro, played a long-divorced couple who, for the sake of their adopted son’s wedding and his very religious biological mother, pretend they are still married. The film received largely negative reviews. In his New York Post review Lou Lumenick wrote, “the brutally unfunny, cringe-worthy The Big Wedding provides ample opportunities for Robert De Niro, Diane Keaton, Susan Sarandon, and Robin Williams to embarrass themselves”.

Keaton wrote her first memoir, Then Again, for Random House in November 2011. Much of the autobiography relies on her mother’s private journals, which include the line “Diane…is a mystery…At times, she’s so basic, at others so wise it frightens me.” In 2012 Keaton’s audiobook recording of Joan Didion’s Slouching Towards Bethlehem was released on Audible.com. Her performance was nominated for a 2013 Audie Award in the Short Stories/Collections category.

In 2014 Keaton starred in And So It Goes and 5 Flights Up. In Rob Reiner’s romantic dramedy And So It Goes, Keaton portrayed a widowed lounge singer who finds autumnal love with a bad boy (Michael Douglas). The film received largely negative reviews. One critic wrote that “And So It Goes aims for comedy, but with two talented actors stuck in a half-hearted effort from a once-mighty filmmaker, it ends in unintentional tragedy.” Keaton co-starred with Morgan Freeman in Richard Loncraine’s comedy film 5 Flights Up, based on Jill Ciment’s novel Heroic Measures. They play a long-married couple who have an eventful weekend after they are forced to contemplate selling their beloved Brooklyn apartment. Shot in New York, the film premiered, under its former name Ruth & Alex, at the 2014 Toronto International Film Festival. The same year Keaton became the first woman to receive the Golden Lion Award at the Zurich Film Festival.

Keaton’s only film of 2015 was Love the Coopers, an ensemble comedy about a troubled family getting together for Christmas, for which she reunited with Because I Said So writer Jessie Nelson. Also starring John Goodman, Ed Helms, and Marisa Tomei, Keaton was attached for several years before the film went into production. Her cast was instrumental in financing and recruiting most other actors, which led her to an executive producer credit in the film. Love the Coopers received largely negative reviews from critics, who called it a “bittersweet blend of holiday cheer”, and became a moderate commercial success at a worldwide total of US$41.1 million against a budget of US$17 million. Also in 2015 Netflix announced the comedy Divanation, for which Keaton was expected to reunite with her First Wives Club co-stars Midler and Hawn to portray a former singing group, but the project failed to materialize.

In 2017 Keaton appeared opposite Brendan Gleeson in the British dramedy film Hampstead. Based on the life of Harry Hallowes, it depicts an American widow (Keaton) who helps a local man defending his ramshackle hut and the life he has been leading on Hampstead Heath for 17 years. The specialty release had a mixed reception from critics, who were unimpressed by the film’s “deeply mediocre story”, but became a minor commercial success. Keaton’s only project of 2018 was Book Club, in which she, Jane Fonda, Candice Bergen, and Mary Steenburgen play four friends who read Fifty Shades of Grey as part of their monthly book club and subsequently begin to change how they view their personal relationships. The romantic comedy received mixed reviews from critics, who felt that Book Club only “intermittently rises to the level of its impressive veteran cast,” but with a worldwide gross of over $91 million, became Keaton’s biggest commercial success in a non-voice role since 2003’s Something’s Gotta Give.

When asked what made Keaton funny, Allen said: “My opinion is that with the exception of Judy Holliday, she’s the finest screen comedienne we’ve ever seen. It’s in her intonation; you can’t quantify it easily. When Groucho Marx or W.C. Fields or Holliday would say something, it’s in the ring of their voices, and she has that. It’s never line comedy with her. It’s all character comedy.” Charles Shyer, who directed her in Baby Boom, said Keaton was “in the mold of the iconic comedic actresses Carole Lombard, Irene Dunne and Rosalind Russell.” In 2017 Keaton was chosen to by the board of directors of the American Film Institute to receive the AFI Life Achievement Award, which Woody Allen presented.