The billionaire tried the drug while being interviewed by American comedian and TV host Joe Rogan. The Tesla CEO also knocked back a whiskey with ice, emphasizing that alcohol is also a drug.
"It's legal, right?" Musk asked before taking a hit.
He also noted that he had tried marijuana before.
Rogan suggested that Musk couldn't afford to use drugs because of the company's shareholders, to which he replied that this was entirely legal.
Musk and Rogan discussed electric planes, sustainable energy, and the process of developing artificial intelligence.
Network users and journalists earlier suggested that Musk is an active drug user after a tweet by a businessman surfaced about the Tesla share price of $420, recalling the number denotes popular slang for marijuana use.
However, Musk refuted the speculation, saying that drugs do not influence his effectiveness.
The use of marijuana for recreational purposes is legal in the US state of California, according to a law that came into force on January 1, 2018.