But the Florida Republican stopped short of saying Congress should subpoena those returns.
Gaetz, a first-term congressman from the Sunshine State's panhandle, has stood by Trump, campaigning with him over the past weekend and closing his raucous one-hour town hall at the Oops Bowling Alley here Thursday night by saying he wanted to "make America great again."
But he surprised the audience when he said, "Absolutely, Donald Trump should release his tax returns."
Donna Waters, a 56-year-old lawyer from Pensacola, became emotional Thursday night as she pressed Gaetz for an answer.
"I'm the descendant of an immigrant, he came to America in 1607 to a town called Jamestown, and my family's been here ever since," Waters said, noting that her family members have fought in every major US war, including both sides of the Civil War.
"Whenever there's a threat to this country, my family has stepped forward," Waters said, tearing up. "There are allegations that a hostile foreign country is committing acts of undeclared war by infiltrating the highest levels of our government."
Waters continued: "You are on the Judiciary Committee. You have said they are going to investigate the Russian allegations. Yes or no, Yes or no -- let me ask my question -- will you call for the release of President Trump's income tax returns?"
As Gaetz took back the microphone, the crowd immediately began screaming, "Yes or no! Yes or no!"
Then Gaetz said, "If you hear me out, you'll like my answer," and called for Trump's returns. The line garnered some rare applause from the crowd that was otherwise mostly livid over Gaetz's push to abolish the Environmental Protection Agency and a string of other issues.
During his presidential campaign, Trump became the first major-party nominee since 1972 not to release his tax returns -- citing ongoing IRS audits and saying he would do so once those audits were completed.
But last month, top Trump adviser Kellyanne Conway said
the President will not release his returns. Conway later sought to clarify her remarks, asserting there had been no change in position from the campaign and that Trump's business advisers had urged him not to release the documents.
Throughout Gaetz's hour-long town hall here just outside of Pensacola, protesters booed, chanted, yelled over him and jeered Gaetz. At one point, a questioner asked Gaetz if he would vote to impeach Trump, to which the crowd began chanting, "Impeach Trump! Impeach Trump!"
"I do not agree with President Trump on every issue, I do not agree with any human being on Planet Earth on every issue, but I support President Trump and I'm going to back him up," Gaetz said.
Gaetz often spoke directly with the protesters. Outside a meeting with constituents at the Santa Rosa County Building, Sarah Coutu, a mother of eight from Milton and member of Florida Panhandle Progressives, confronted him on his EPA bill.
As he attempted to talk through his call to abolish the EPA, protesters screamed, "Your last term!" over him and he walked into the building.
But Gaetz also tightly controlled access to his earlier events, holding an earlier meeting with constituents in a back room of a restaurant that had limited access.
During a stop at Grover T's BBQ in Milton, Florida, Gaetz was ushered past more than 100 protesters by a group of sheriff's deputies and members of Bikers for Trump, who said they were providing security.