He was also charged with illegally possessing weapons, which he had possessed for only 11 days in October that year.
The president's son, who has written openly about his addiction, claimed he didn't consider himself a drug addict when he purchased the revolver.
Hunter Biden could face up to 25 years in prison, though he is unlikely to serve time for a first offense.
He has long been a target of far-right Republicans, and Trump allies have long investigated him in Congress over allegations of corruption and influence-peddling. He has never been charged.
Hunter Biden's business dealings in China and Ukraine also formed the basis of efforts by Republican lawmakers to launch impeachment proceedings against his father. Those efforts also went nowhere.
The White House has said there will be no presidential pardon for Hunter Biden.