Sylvester Stallone's son Sage died from natural causes due to a heart condition, the Los Angeles County Coroner has ruled.
Sage Stallone was found dead at his Hollywood home by an employee and a relative on 13 July.
Bottles of prescription pills were found but it was not clear if they were connected with his death.
Officials said on Thursday that the 36-year-old died due to a condition that causes blockage of the arteries.
Toxicology results showed Stallone had a only a small amount of the sedative hydrocodone in his body.
No other drugs were detected and the death has been classified a natural death.
The actor and film director's sudden death stunned his family and friends.
Sylvester Stallone's publicist described him as "devastated and grief-stricken" and the actor skipped several promotional events for his film The Expendables 2.
Sage Moonblood Stallone was the oldest of Sylvester Stallone's children and co-starred with his father in two films, Rocky V and Daylight.
He also became involved in movie-making, directing a 2006 short, Vic, that was screened at the Palm Springs Film Festival.
In 1996 the young Stallone co-founded Grindhouse Releasing, a company dedicated to preserving and promoting the B-movies and exploitation films of the 1970s and '80s.
Sylvester Stallone's spokeswoman said the actor had no comment about the coroner's findings.