Earlier in the day, Trump said a peace deal with Iran was now “complete,” framing the announcement as part of what he described as a historic day.
The UFC event, branded “UFC Freedom 250,” featured 14 fighters competing in an Octagon-style cage. Brazil’s Diego Lopes won the opening bout by knockout.
Trump also appeared on the Truman balcony, saluting as the national anthem played and 12 US military aircraft conducted a flyover of the White House.
The event, which coincided with Flag Day and celebrations tied to the 250th anniversary of US independence, was briefly delayed due to thunderstorms in Washington.
Critics condemned the spectacle as inappropriate for the White House, pointing to the commercialization of the event and its staging during ongoing tensions with Iran that have affected global energy prices.
Supporters at a public viewing area near the Ellipse defended the celebration.
“I do think maybe it's like a little bit of selfishness, but he is the leader, so he has a say," said Nyles Rife, a 35-year-old sports performance coach from Virginia.
"If I was a president, if I were to have a UFC event on my birthday, and it fell on the 250th anniversary/Flag day, I'd do the same. Why not?” he added.
Mark Toone, a 50-year-old US Marine Corps veteran, said the event reflected American culture.
"I think that it's unfortunate that the opposition is spreading lots of lies and untruths about this event," he said.
The White House said the UFC covered the full cost of the event.
The celebration comes as Trump, the oldest US president to take office, has faced renewed scrutiny over his health. He has previously acknowledged discomfort about aging, saying in a recent video, “It's not a number I like, but I'm here nevertheless.”