A used hypodermic needle and a spoon with drug residue were present in the room where Cory Monteith died in July, the final coroner's report has found.
The report confirmed the Glee star died from using intravenous heroin combined with alcohol.
Coroner Claire Thompson confirmed the death was "accidental".
She said in her report: "Mr Monteith was found in a collapsed position on the hotel room floor. It appeared that Mr Monteith had been dead for several hours."
Two empty bottles of champagne were also found in his room.
Monteith was found dead in his hotel room in Vancouver on 13 July, the day he was due to check out.
The investigation said Monteith had a history of illicit drug use with periods of rehabilitation and abstinence from drugs.
Monteith talked openly about struggling with addiction since he was a teenager. He told Parade magazine in 2011 he was "lucky to be alive".
In the interview, he said he had been using marijuana and alcohol since the age of 13, and his drug use was "out of control" by the time he was 16.
In April he admitted himself to a rehabilitation clinic for substance addiction.
Monteith starred as quarterback-turned-singer Finn Hudson in the hit high school musical drama Glee.
The late actor was honoured with a tribute led by co-star Jane Lynch during last week’s Emmy Awards.