His big break came when he was nominated for an Academy award for Best Actor for his role as teacher Jaime Escalante in the movie Stand and Deliver. He went on to American TV playing the character of Lt. Martin Castillo on the popular 80's TV series Miami Vice, starring opposite Don Johnson and Philip Michael Thomas. He was twice nominated for an Emmy for best supporting actor for this role, and won once.
In recent years, he has won quite a fan following for his role as Commander Adama on the Sci-Fi network's re-imagined Battlestar Galactica series.
Olmos has stated in interviews that he was initially asked to work the two episodes of The West Wing he appeared in for scale, since the producers felt that they had a top-rated show and that any guest stars would benefit from the exposure they received on the show, and they should be grateful for the opportunity.