He first broke through the mainstream in 1997 with a performance as tagger César Sánchez in the film One Eight Seven. In 1998, he was in Ray Bradbury's cult film The Wonderful Ice Cream Suit. He next portrayed a gay hitman named Francisco "Frankie Flowers" Flores for the Mexican drug cartels in Steven Soderbergh's 2000 ensemble drama Traffic. For his portrayal of a USMC prisoner in the 2001 film The Last Castle Collins was nominated for the 2002 American Latino Media Arts (ALMA) Award for Best Supporting Actor in a motion picture. In 2002, he played the role of Buddy in the film Confessions of an American Girl. In 2005, Collins won rave reviews for his subtle portrayal of killer Perry Smith in the fact-based film Capote, which was nominated for the Academy Award for Best Picture in 2006. He starred in the 2005 film Dirty alongside Oscar winner Cuba Gooding Jr. Collins starred on FX Networks' series Thief and received an Emmy nomination. Collins also played a supporting role on FX Networks' series The Shield as undercover ICE agent Hernan. He also has a small role in 2006's Babel, directed by Alejandro González Iñárritu.