There is no evidence to suggest the 31-year-old actor’s death was anything more than a “sad and tragic accident”, officials say.
Glee star Cory Monteith died from a heroin and alcohol overdose, according to a coroner.
The 31-year-old actor was found dead in his hotel room in the Canadian city of Vancouver on Saturday.
Barbara McLintock, from the British Columbia coroner’s office, said: “There is no evidence to suggest Mr Monteith’s death was anything other than a most sad and tragic accident.
“The cause of death was a mixed drug toxicity, and it involved heroin primarily and also alcohol.”
The findings come after a post-mortem examination and toxicological analysis.
Police said the Canadian actor had been out with other people earlier, but was believed to have been alone when he died.
He was discovered by hotel staff after he failed to check out on Saturday.
The coroner’s office said the investigation into his death was continuing, and no other details were available at this time.
Monteith had talked openly about struggling with addiction since he was a teenager, calling it a serious problem and telling Parade magazine in 2011 he was “lucky to be alive”.
The star, who played Finn Hudson in the TV show and dated his co-star Lea Michele, admitted himself to rehab in April.
He also received treatment when he was 19.
Monteith and the other Glee actors became high-profile celebrities when the hit musical show made its TV debut in 2009.
The Fox network and the producers of Glee, including 20th Century Fox Television, said Monteith was an exceptional performer “and an even more exceptional person”.
Gia Milani, who recently produced and directed a Canadian film featuring Monteith, said the actor “seemed healthy” when she last saw him four weeks ago in Los Angeles.
“He looked super fit and he was energetic and excited,” Milani said.
She said Monteith showed no signs of a substance abuse problem while shooting the film a year ago.