Chaffetz has attended two Romney fundraisers so far this year and spoke highly of the former 2002 Salt Lake Olympic leader's chances for the presidency, though the Utah congressman had refused to endorse him until now. Romney has also helped Chaffetz raise money for his own campaigns.
Chaffetz, a two-term congressman, said he deferred announcing his endorsement until he could have a personal conversation with Huntsman, who had picked the virtually unknown Republican to run his gubernatorial campaign in 2004.
"It's nothing against Huntsman; he's been very good to me," Chaffetz said. "I had this discussion with Jon last week. It was tough for me, but I was honest and candid that I'm going to support Mitt Romney."
Romney's campaign did not immediately respond to a request for comment. Huntsman's campaign declined any comment on Chaffetz's endorsement.
He is the second big-name Utahn to line up behind Romney in recent weeks. Utah Attorney General Mark Shurtleff, who served alongside Huntsman for nearly five years, previously offered his backing to Romney.