Mulaney’s parents attended Georgetown University and Yale Law School. They were at Yale at the same time as future president Bill Clinton; Mulaney met Clinton in 1992. Growing up, Mulaney was an altar boy. He is the third of five children. He has two brothers, one of whom is deceased, and two sisters.

From watching the lifestyle of the character Ricky Ricardo on the program I Love Lucy, Mulaney knew he wanted to go into show business at the age of five. At the age of seven, Mulaney had an opportunity to audition for the role of Kevin in the film Home Alone, but his parents declined. For junior high, he attended St. Clement School where, in lieu of doing reports he and his best friend, John O’Brien, would offer to perform what they had learned in the format of a skit. Mulaney would also frequent the Museum of Broadcast Communications, where he would watch archived episodes of shows such as I Love Lucy or The Tonight Show Starring Johnny Carson. He attended St. Ignatius College Prep where he graduated in 2000. Mulaney then enrolled at his parents’ alma mater, Georgetown University, where he studied English literature and religion. He joined the school’s improv group, and met Nick Kroll and Mike Birbiglia. He later joined Birbiglia on his stand-up tour, which improved his stage presence.

After graduating from Georgetown in 2004, Mulaney moved to New York City with ambitions of a career in comedy, and was hired as an office assistant at Comedy Central. After a year, he pitched the idea for a parody of the I Love the ’80s called I Love the ’30s, which he developed along with fellow comedian Nick Kroll. Mulaney was working at the network when Dave Chappelle abruptly left the network. Initially, the network had planned to fly John out to Los Angeles in order to secure the tapes for season three of the eponymous show; however, feeling it was a “hindrance to being a comedian”, he instead quit and started working freelance.

After being discovered while performing on Late Night with Conan O’Brien, Mulaney was asked to audition for Saturday Night Live in August 2008, along with Kroll, Donald Glover, Ellie Kemper, T.J. Miller and Bobby Moynihan. Unusual for an SNL audition, Mulaney did not prepare any impressions, instead performing standup with “charactery bits in them”. He went in with little expectations, although he thought it’d be a “cool story”. Mulaney won a spot on the writing team, where he remained for four seasons. He also occasionally appeared on the show’s Weekend Update segment. He and SNL actor Bill Hader co-created the recurring SNL character Stefon. Mulaney was nominated for the Primetime Emmy Award for Outstanding Writing for a Variety Series with the SNL writing staff from 2009 to 2012. Mulaney won a Primetime Emmy Award for Outstanding Original Music and Lyrics at the 63rd Primetime Emmy Awards with Justin Timberlake, Seth Meyers and Katreese Barnes. Mulaney returned to host Saturday Night Live four times: on April 14, 2018; March 2, 2019; February 29, 2020; and October 31, 2020, respectively, making him the fourth SNL writer (after Conan O’Brien, Louis C.K., and Larry David) to host SNL despite never having been a cast member.

In addition to his work on SNL, Mulaney has worked for 17 years as a stand-up comedian. He has been a headliner since 2008. He has performed on Live at Gotham, Conan, Jimmy Kimmel Live, Late Night With Jimmy Fallon, Late Night With Conan O’Brien, and Comedy Central Presents. Mulaney also released a stand-up comedy album titled The Top Part in 2009 and a stand-up comedy special called New in Town in 2012. Both were produced with Comedy Central. He performed at the 2008 Bonnaroo Music Festival.

Mulaney has received numerous awards nominations and wins for his work in television. In 2009 Mulaney won a Peabody Award alongside the writers of Saturday Night Live for their satirical work on the 2008 United States Presidential Election. He has received many Primetime Emmy Award nominations for his work on Saturday Night Live and Documentary Now!. He won his first Emmy Award in 2011 for co-writing the song, “Justin Timberlake Monologue” with Seth Meyers and Justin Timberlake which aired on Saturday Night Live. He won his second Emmy in 2018 for Outstanding Writing for a Variety Special for his standup special, John Mulaney: Kid Gorgeous at Radio City.

In May 2013, NBC passed on picking up Mulaney’s semi-autobiographical sitcom pilot, titled Mulaney. In June 2013, Fox Broadcasting Company ordered a new script while considering whether to order the production of several episodes. In October 2013, Fox announced that they picked up the show for a six-episode season order. Mulaney was the creator, producer, and writer of his eponymous series until its cancellation in May 2015. Mulaney is quoted as saying he “wanted to do the type of live-audience multi-camera sitcoms that I grew up on.” The series received poor reviews, including playwright and The New York Times TV critic Neil Genzlinger’s, who wrote “It rips off Seinfeld so aggressively that in Episode 2 it even makes fun of its own plagiarism. But one thing it forgot to borrow from Seinfeld was intelligence.”

On July 5, 2014, Mulaney married makeup artist and lampshade artisan Annamarie Tendler. Their wedding ceremony was performed by friend Dan Levy.

Mulaney’s third stand-up comedy special, titled The Comeback Kid, was released on November 13, 2015, on Netflix. His second stand-up show, New in Town, which premiered on Comedy Central in 2012, is also on Netflix. The Comeback Kid received critical acclaim, with David Sims of The Atlantic calling it “a reminder of everything that makes Mulaney so singular: storytelling rich with well-observed details, delivered with the confidence of someone decades older than 33.” In 2016, Mulaney received a nomination for the Primetime Emmy Award for Outstanding Writing for a Variety Special for The Comeback Kid, losing to Patton Oswalt’s Talking for Clapping.

Mulaney regularly performs as George St. Geegland, an elderly man from the Upper West Side of New York. St. Geegland and fellow New Yorker Gil Faizon (portrayed by Georgetown classmate and comedian Nick Kroll), host a prank show called Too Much Tuna in which contestants are given sandwiches with too much tuna fish. Mulaney has toured the United States alongside Kroll in a show called Oh, Hello, with both in character as George St. Geegland and Gil Faizon, respectively. The show premiered on Broadway on September 23, 2016, and concluded its run on January 22, 2017. The Broadway production was filmed and released on Netflix on June 13, 2017. Steve Martin was the celebrity special guest, with a bonus clip showing Michael J. Fox as the guest. Matthew Broderick appeared as himself in a brief cameo towards the end of the special.

Following his tenure at Saturday Night Live, Mulaney contributed writing to other TV projects, including Maya & Marty; Documentary Now!; Oh, Hello on Broadway; and the Comedy Central Roast of James Franco. He also acted in supporting roles on television shows such as Crashing, Portlandia, and Difficult People. Mulaney currently provides the voice of a lead character on the animated Netflix series Big Mouth alongside his writing partner Nick Kroll, who co-created the show. Together with Nick Kroll, Mulaney also co-hosted the Independent Spirit Awards ceremonies in 2017 and 2018. In 2018, Mulaney provided the voice of Spider-Ham in the Academy Award-winning animated film Spider-Man: Into the Spider-Verse. He also appeared in a Netflix and YouTube collaboration series hosted by Tan France, Dressing Funny, in June 2019. In November 2020, Late Night with Seth Meyers producer Mike Shoemaker announced that Mulaney had joined the show as a staff writer.

Mulaney’s fourth stand-up comedy tour, Kid Gorgeous, kicked off its first leg in May 2017, concluding in July of that year. A second leg began in September 2017 in Colorado Springs, Colorado and concluded in April 2018 in Jacksonville, Florida. The tour featured seven shows at Radio City Music Hall in New York City in February 2018, one of which was filmed for another Netflix special. Kid Gorgeous was met with critical acclaim, with Steve Greene of IndieWire calling it “one of the year’s best pieces of writing.” At the 70th Primetime Emmy Awards, Mulaney received an Emmy for Outstanding Writing for a Variety Special for Kid Gorgeous.

In 2017, he was invited to appear alongside Steve Martin, Martin Short, Bill Murray, Jimmy Kimmel, and Norm MacDonald to honor David Letterman, who was accepting The Mark Twain Prize for American Humor at The Kennedy Center. When accepting the prize, Letterman stated, “John Mulaney, this is the future of comedy, ladies and gentlemen.”

In January 2019, it was announced that Mulaney would be touring with Pete Davidson together in New York, New Jersey, Pennsylvania and Massachusetts for a limited series of comedy shows titled “Sundays with Pete & John.” Mulaney and Davidson have become close, appearing together on The Tonight Show with Jimmy Fallon and Saturday Night Live.

In December 2019, Mulaney released a children’s musical comedy special titled John Mulaney & the Sack Lunch Bunch on Netflix. The special was inspired by Sesame Street, Mister Rogers’ Neighborhood, The Electric Company, Free to Be… You and Me, and 3-2-1 Contact. The special features Mulaney, along with fifteen child actors and singers, aged 8 to 13. Celebrity cameos include Tony Award winner André De Shields, David Byrne, Richard Kind, Natasha Lyonne, Annaleigh Ashford, and Jake Gyllenhaal as “Mr. Music”. The special has been universally praised, receiving a 96% fresh score on Rotten Tomatoes. Critic Alan Sepinwall of Rolling Stone Magazine, wrote “It is, like Galaxy Quest, or The Princess Bride, one of those gems that manages to simultaneously parody a genre and be an excellent recreation of it.” In 2020, Mulaney received two Primetime Emmy nominations for Outstanding Variety Special (Pre-Recorded) and Outstanding Writing for a Variety Special for his work on the special.

Mulaney comes from a political family on his mother’s side. During an interview with Esquire magazine from September 12, 2019, Mulaney stated that he donated to the Bernie Sanders 2016 presidential campaign. On June 2, 2020, Mulaney was seen with his wife at a Black Lives Matter protest in Washington D.C.