According to the Office of the Chief Medical Examiner of New York City via Us Weekly the 46-year-old actor died of "accidental acute mixed-drug intoxication, including heroin, cocaine, benzodiazepines and amphetamine."
The Capote star was found dead on Sunday, February 2 in his New York City apartment.
At the time, authorities found as many as 65 bags of heroin at his house, along with syringes and prescription drugs.
Hoffman was finishing his scenes for the last installment of the Hunger Games saga, Mockingjay Part 2 and was set to direct Ezekiel Moss, a ghost story starring Amy Adams and Jake Gyllenhaal, before his death.
He is survived by his partner of 14 years, Mimi O'Donnell, and his three children -- son Cooper and daughters Tallulah and Willa.