In the late 1960s and the early 1970s, he 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. 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. In 1971, Olmos married Katija Keel, the daughter of actor Howard Keel. They had two children, Bodie and Mico, before divorcing in 1992. He also has three adopted children-- Michael, Brandon and Tamiko.
In 1980, he was cast in the post-apocalyptic science fiction film (now a Japanese cult classic) Virus (復活の日 Fukkatsu no hi-- directed by Kinji Fukasaku and based on a novel written by Sakyo Komatsu), where he acted opposite Robert Vaughn, Chuck Connors, Olivia Hussey, Ken Ogata, Sonny Chiba and Glenn Ford. Most remarkable was Olmos playing 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.
From 1984 to 1989, he starred in his biggest role up to that date as the taciturn police Lieutenant Martín Castillo in the television series "Miami Vice," opposite Don Johnson and Philip Michael Thomas. He was awarded a Golden Globe and an Emmy in 1985 for his work in the series.
Returning to film, he became the first American-born Latino 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 multigenerational story of a Chicano family. In 1997, he starred alongside Jennifer López in the film Selena. He 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 Latino Los Angeles-based family in the PBS drama "American Family: Journey of Dreams."
From 2003 to 2009, he starred as Commander (later Admiral) 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, as well as directed a television movie based upon the show, The Plan. Asteroid 5608 Olmos is named in his honor.
In 2006, he co-produced, directed, and played the bit part of Julián Nava in the HBO movie about the 1968 Chicano Blowouts, Walkout. He also appeared in Snoop Dogg's music video "Vato," featuring B-Real from Cypress Hill. In the series finale of the ABC sitcom "George López," he guest-starred as the plant's new multimillionaire owner.
He has often been involved in social activism, especially that affecting the Latino community. During the 1992 Los Angeles Riots, when many people left the city, he went out with a broom and worked to get communities cleaned up and rebuilt. In 1997, he co-founded the Los Angeles Latino International Film Festival with Marlene Dermer, George Hernández 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 USA, attended by over 700,000 people. He married actress Lorraine Bracco in 1994. They divorced in 2002. He is currently married to Puerto Rican actress Lymari Nadal.
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 Latinos 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 Latino stereotypes and transcend the normal stigmas of most Latino-oriented movies. In 1999, he 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 appeared on Puerto Rican television to blame the Puerto Rican and United States governments for not cleaning Vieques after the U.S. Navy stopped using the island for bombing practice.