As Mr Romney took the stage at a state party convention of about 2,100 people in West Valley City, delegates shouted that he was a "traitor" and a "communist".
Mitt Romney is one of a handful of senior GOP officials who refused to endorse Donald Trump in 2016, calling him a "phony" and a "fraud", while the 45th president called the Utah senator "one of the dumbest and worst candidates in the history of Republican politics".
Mr Romney, a former presidential nominee, was the only Republican to vote twice to impeach Mr Trump. Romney responded, per NBC: "Oh yeah, you can boo all you like, but I've been a Republican all my life". He then called on the party to come together in strength and unity.
The Senate ultimately voted 57-43 to acquit the former president, failing to meet the 67-vote threshold to convict.
The incident is another example of the grip the former president has on the Republican Party and the treatment Romney, a moderate member of the GOP, has faced for his criticisms and rebukes of Trump.
Meanwhile, speculation is growing that the Republican Party will seek to oust Wyoming Congressmember Liz Cheney from her leadership role. 'And she did what she felt was right. "We need to have room for a variety of views, especially since we adhere to those core principles that I mentioned earlier".
Cheney was the highest-ranking Republican in the House to vote in favor of impeaching Trump for the second time.
The move by Romney garnered backlash from the party and Trump himself.
'Heartwarming to read new polls on big-shot warmonger Liz Cheney of the great State of Wyoming. 'They never liked her much, but I say she'll never run in a Wyoming election again!'