The younger Biden issued a statement saying he learned of the probe Tuesday.
"I learned yesterday for the first time that the U.S. Attorney's Office in Delaware advised by legal counsel, also yesterday, that they are investigating my tax affairs," he said. "I take this matter very seriously but I am confident that a professional and objective review of these matters will demonstrate that I handled my affairs legally and appropriately, including with the benefit of professional tax advisors."
The Biden transition team sent out its own statement in response to the news.
"President-elect Biden is deeply proud of his son, who has fought through difficult challenges, including the vicious personal attacks of recent months, only to emerge stronger," the statement read.
The team didn't offer further information about the nature of the investigation or its scope.
The Biden family has previously faced scrutiny for Hunter Biden's history with drug addiction and a paternity lawsuit in Arkansas. He was also the subject of accusations by President Donald Trump and his supporters, who said there was impropriety in Hunter Biden's work for Ukrainian natural gas company Burisma.