Darren Salter, senior coroner for the county of Oxfordshire in southern England, said a postmortem examination found that the singer died of "dilated cardiomyopathy with myocarditis and fatty liver."
Dilated cardiomyopathy is a condition in which the left ventricle of the heart becomes stretched and weakened, limiting the heart's ability to pump blood. Myocarditis is inflammation of the heart muscle.
The former Wham! singer-songwriter was found dead at his country home in Oxfordshire on Dec. 25. He was 53.
An initial autopsy failed to determine the cause of death.
Salter said that because Michael died of natural causes, there will be no coroner's inquest or further inquiries.
Police initially investigated and took witness statements in order to establish the facts of Michael's death, which they called "unexplained but non-suspicious."
Wham!, formed by Michael and Andrew Ridgeley, topped the charts in the 1980s with exuberant pop hits including "Wake Me Up Before You Go-Go" and "Young Guns (Go For It)." Michael went on to a solo career studded with hits including "Careless Whisper" and "Freedom" and sold more than 100 million albums around the world.
He also suffered problems with drugs and alcohol, and in 2010 was briefly jailed after crashing his car into a shop front near his London home.
Michael's death prompted an outpouring of recognition for his musical gifts as well as his charitable work in support of anti-AIDS groups, cancer research charities and Childline, which offers confidential phone counseling for young people.
6:15 a.m.: This article was updated with details of Michael's career and death.