Fighters, promoters and television streamers all stand to gain from the Ultimate Fighting Championship bout that President Trump is hosting on the South Lawn of the White House on Sunday.

As a small investor in TKO Group Holdings, U.F.C.’s parent company, the president could benefit as well.

In March, one of Mr. Trump’s brokerage accounts purchased between $15,000 and $50,000 in shares of the company, according to a recently released financial disclosure. A Trump account also held a small number of shares in TKO Group as of 2024, another disclosure form shows.

Ethics groups have lamented that the president is using government land to hold an event that could theoretically benefit him. One group sued, seeking to block the fight, and cited Mr. Trump’s shares in TKO Group. A judge ruled on Friday that the bout could proceed.

The shares represent a tiny fraction of Mr. Trump’s overall investment portfolio, which is worth hundreds of millions of dollars and spans hundreds of stocks and bonds. The precise size of Mr. Trump’s stake in TKO Group, and whether it has changed since March, is unknown.

There is also no indication that the president was involved in the trade.

Mr. Trump’s family business, the Trump Organization, has said that the president has no control over trades in his brokerage accounts. Rather, the company says that these were automated trades placed by outside financial institutions that have full authority over the accounts.

“Neither President Trump, his family, nor the Trump Organization has any role in selecting, directing, approving, influencing or soliciting specific investments,” the Trump Organization said in a statement. “They receive no advance notice of trades, cannot alter or override the managers’ strategies or models, and provide no input regarding investment decisions or portfolio operations.”

The company said it had created this buffer to mitigate ethical concerns.

“This structure was intentionally designed to maintain a clear separation between President Trump and the independent third party investment managers overseeing the accounts, and avoid even the appearance of any conflict of interest,” the company said in the statement.

The fight on Sunday, which the president is holding on his 80th birthday and in honor of the nation’s 250th birthday, is expected to be a big moneymaker for U.F.C. and other Trump allies.

Paramount Skydance, the media company owned by Larry and David Ellison, who are friendly with the president, is streaming the event.

It is unclear, however, whether Mr. Trump and other TKO Group shareholders will immediately benefit. The stock was down more than 4 percent on Friday.