Former Anthrax frontman Dan Nelson was busted Wednesday for thrashing a 74-year-old man inside a Queens hotel last month, according to cops.

Nelson — who helmed the NYC-born, thrash-metal outfit between 2007 and 2009 — got heated when the elderly man asked him a question at the Aloft New York LaGuardia Airport hotel in East Elmhurst around 11 p.m. on Aug. 30, police said.

The 43-year-old vocalist allegedly pummeled the oldster and then scrammed. He turned himself over to police at the 115th Precinct at 8 a.m. Wednesday, where he was charged with assault and harassment, cops said.

Nelson, of Levittown, LI, was awaiting arraignment in Queens Criminal Court on Wednesday night.

He could not be reached for comment.

Nelson, who had credits on Anthrax’s 2011 album “Worship Music” actually departed the band in 2009.

He sued his former bandmates for defamation to the tune of $2.65 million when they said publicly he left because of health reasons. They settled for an undisclosed amount in 2012.