Valium, morphine, marijuana and an elevated level of codeine were all found in Chris Penn's body when he died, according to the toxicology report obtained by Access Hollywood.
The report also found traces of promethazine (an antihistamine) in his system.
Chris, the younger brother of Oscar-winner Sean Penn, was found dead on January 24 at his condominium near the beach in Santa Monica, California.
The 40-year-old actor's body was discovered after police were called to the condominium complex by Penn's housekeeper.
The official cause of death is still an enlarged heart, but the coroner's office claims the drugs in his system added to the problems associated with his already enlarged heart.
Chris Penn's film credits included "Starsky & Hutch," "Mulholland Falls," "Rumble Fish," "All the Right Moves," "Footloose" and "Rush Hour." He also played Nice Guy Eddie Cabot in the 1992 Quentin Tarantino crime drama "Reservoir Dogs."
His late father, Leo Penn, directed television shows. His mother, Eileen Ryan, is an actress whose credits include "I Am Sam," "Magnolia" and "Parenthood." Another brother is musician Michael Penn.
Chris' latest film, "The Darwin Awards," premiered in late January the Sundance Film Festival.