Mac Miller died of an accidental overdose of fentanyl, cocaine and alcohol, according to the coroner.
Miller's personal assistant, making a daily visit to Miller's home in the San Fernando Valley section of Los Angeles, found him unresponsive on his bed at about 11:30 a.m. on September 7, the report states.
His death was also characterised as accidental. He was found by his assistant in a "praying position", kneeling forward with his face on his knees.
Authorities performed an autopsy on Miller the following day but "a cause of death was deferred pending further investigation", the medical examiner's office said in a release. He was already "blue" when someone called 911.
An empty bottle of alcohol was found on the nightstand, near Mac's body. and a bottle of prescription pills was found in the bathroom.
Cops found a rolled-up $20 bill with white powdery residue in Mac's right pocket.
Miller, whose full name is Malcolm James McCormick, had battled with substance abuse for years, according to several reports. He was found unresponsive and pronounced dead at the scene. Participating acts included Chance the Rapper, John Mayer and SZA.
Miller's death came just months after he split from Ariana Grande and weeks after he was charged with a DUI.