He graduated from Montebello High School in 1964. While at Montebello High School, he lost a race for Student Body President to future California Democratic Party Chair Art Torres. In his teen years, he was the lead singer for a band he named Pacific Ocean, so called because it was to be “the biggest thing on the West Coast”. For several years, Pacific Ocean performed at various clubs in and around Los Angeles, and released their only record, Purgatory, in 1968. At the same time, he attended classes at East Los Angeles College, including courses in acting.

From 1979 to 1987, Olmos lived in West New York, New Jersey. In 1971, he married Kaija Keel, the daughter of actor Howard Keel. They had two children, Bodie and Mico, before divorcing in 1992. Olmos has four adopted children: Daniela, Michael, Brandon, and Tamiko. He married actress Lorraine Bracco in 1994. She filed for divorce in January 2002 after five years of separation. Olmos also had a long term relationship with actress Lymari Nadal. They married in 2002, and separated in 2013.

In 1980, Olmos was cast in the post-apocalyptic science fiction film Virus (復活の日 Fukkatsu no Hi), directed by Kinji Fukasaku and based on a novel written by Sakyo Komatsu. His role required him to play a piano while singing a Spanish ballad during the later part of the film. Although not a box office success, Virus was notable for being the most expensive Japanese film ever made at the time.

In the late 1960s and the early 1970s, Olmos branched out from music into acting, appearing in many small productions, until his big break portraying the narrator, called “El Pachuco,” in the play Zoot Suit, which dramatized the World War II-era rioting in California brought about by the tensions between Mexican-Americans and local police. (See Zoot Suit Riots.) The play moved to Broadway, and Olmos earned a Tony Award nomination. He subsequently took the role to the filmed version in 1981, and appeared in many other films including Wolfen, Blade Runner and The Ballad of Gregorio Cortez.

From 1984 to 1989, he starred in his biggest role up to that date as the taciturn police Lieutenant Martin Castillo in the television series Miami Vice, opposite Don Johnson and Philip Michael Thomas, for which he was awarded a Golden Globe and an Emmy in 1985. At this time, Olmos also starred in a short training video for the United States Postal Service entitled Was it Worth It?, a video about theft in the workplace. He was contacted about playing the captain of the USS Enterprise (NCC-1701-D) on Star Trek: The Next Generation when it was in pre-production in 1986, but declined.

Returning to film, Olmos became the first American-born Hispanic to receive an Academy Award nomination for Best Actor, in Stand and Deliver, for his portrayal of real-life math teacher, Jaime Escalante. He directed and starred in American Me in 1992, and also starred in My Family/Mi Familia, a multi-generational story of a Chicano family. He had a slight appearance in the video of the American rock band Toto, “I Will Remember” (1995), where he can be seen with actor Miguel Ferrer. In 1997, he starred alongside Jennifer Lopez in the film Selena. Olmos played Dominican Republic dictator Rafael Leónidas Trujillo in the 2001 movie In the Time of the Butterflies. He also had a recurring role as U.S. Supreme Court Justice Roberto Mendoza in the NBC drama The West Wing. From 2002 to 2004, he starred as a recently widowed father of a Hispanic L.A.-family in the PBS drama American Family: Journey of Dreams.

In 1992, a woman accused Olmos of twice touching her in a sexual manner while they watched TV and flirted together. Olmos paid the family a cash settlement of $150,000 in response to the allegations, but denied that they were true. He claimed that the settlement was in fact meant to protect his son, Bodie Olmos, not him.

In 1993, Olmos was awarded an honorary Doctor of Humane Letters (L.H.D.) degree from Whittier College.

In 1996, he was awarded an honorary Doctorate of Fine Arts from California State University, Fresno. In 2007, after a seven-year process, he obtained Mexican nationality. Asteroid 5608 Olmos is named in his honor.

Olmos has often been involved in social activism, especially that affecting the U.S. Hispanic community. During the 1992 Rodney King Riots in Los Angeles, Olmos went out with a broom and worked to get communities cleaned up and rebuilt. He also attended an Oprah episode relating to the L.A. riots as an audience member. In 1997, he co-founded the Los Angeles Latino International Film Festival with Marlene Dermer, George Hernandez and Kirk Whisler. That same year, he co-founded with Kirk Whisler the non-profit organization, Latino Literacy Now, that has produced Latino Book & Festivals around the US, attended by over 700,000 people.

In 1997, a woman accused Olmos of sexually assaulting her in a South Carolina hotel room.

In 1998, he founded Latino Public Broadcasting and currently serves as its chairman. Latino Public Broadcasting funds public television programming that focuses on issues affecting Hispanics and advocates for diverse perspectives in public television. That same year, he starred in The Wonderful Ice Cream Suit, a comedy that sought to break Hispanic stereotypes and transcend the normal stigmas of most Hispanic-oriented movies. In 1999, Olmos was one of the driving forces that created Americanos: Latino Life in the U.S., a book project featuring over 30 award-winning photographers, later turned into a Smithsonian traveling exhibition, music CD and HBO special.

He also makes frequent appearances at juvenile halls and detention centers to speak to at-risk teenagers. He has also been an international ambassador for UNICEF. In 2001, he was arrested and spent 20 days in jail for taking part in the Navy-Vieques protests against United States Navy target practice bombings of the island of Vieques, Puerto Rico. On January 5, 2007, he blamed the United States government for not cleaning Vieques after the U.S. Navy stopped using the island for bombing practice.

From 2003 to 2009, he starred as Commander William Adama in the Sci-Fi Channel’s reimagined Battlestar Galactica miniseries, and in the television series that followed. He directed four episodes of the show, “Tigh Me Up, Tigh Me Down” (1.9), “Taking a Break from All Your Worries” (3.13), “Escape Velocity” (4.4), and “Islanded in a Stream of Stars” (4.18). He also directed a television movie based upon the show, The Plan. Regarding his work on the show, he told CraveOnline, “I’m very grateful for the work that I’ve been able to do in my life, but I can honestly tell you, this is the best usage of television I’ve ever been a part of to date.”

In 2006, he co-produced, directed, and played the bit part of Julian Nava in the HBO movie about the 1968 Chicano Blowouts, Walkout. He also appeared in Snoop Dogg’s music video “Vato”. In the series finale of the ABC sitcom George Lopez, titled “George Decides to Sta-Local Where It’s Familia”; he guest-starred as the plant’s new multi-millionaire owner. More recently, he has been a spokesperson for Farmers Insurance Group, starring in their Spanish language commercials.