The surprising deal on Tuesday ending a civil war in the world of professional golf stands to produce benefits for former President Donald J. Trump’s family business by increasing the prospect of major tournaments continuing to be played at Trump-owned courses in the United States and perhaps abroad.

The outcome is the latest example of how the close relationship between Mr. Trump, the front-runner for the 2024 Republican presidential nomination, and Saudi Arabia, whose sovereign wealth fund is the force behind the upheaval in the golf world, has proved beneficial to both sides even as it has prompted intense ethical scrutiny and political criticism.

Even as it has injected new money and competition into professional golf, Saudi Arabia has been accused of using its wealth to buff its global reputation and obscure its human rights record through sports. That campaign now seems to have yielded business opportunities and a higher profile in the golf world for Mr. Trump as he seeks another term in the White House.

Since the establishment of LIV Golf, the Saudi-funded breakaway professional golf circuit, Mr. Trump and his family have aligned themselves with LIV against the PGA Tour at a time when the golf establishment in the United States and Britain had moved to shut Trump courses out of major professional competitions, a trophy that the Trump family had long sought.

The turn away from Mr. Trump and his courses only accelerated after the Jan. 6, 2021, attack on the Capitol by a pro-Trump mob. Just days after the assault, P.G.A. of America announced it was canceling a planned 2022 tournament at the Trump National Golf Club in Bedminster, N.J., which had been planned for years.

LIV soon became the Trump family’s ticket back into the rarefied world of global tournaments, with events last year at Bedminster and Trump National Doral, the family’s golf resort near Miami. This year LIV brought tournaments to three Trump courses, adding the Trump National Golf Club in Northern Virginia to the schedule.

The decision by professional golf in the United States to shun Mr. Trump had infuriated members of his family. Mr. Trump’s business had spent more than a decade buying up or developing golf courses around the world with the goal of hosting major tournaments, which help drive memberships by putting the courses in the spotlight and could confer a degree of sports-world legitimacy on Mr. Trump, an avid golfer.

Dating back to when Mr. Trump was in the White House, he and his family have had unusually close ties with Saudi Arabia and the royal family there. His first foreign trip as president was to Riyadh, where he received a lavish welcome.

Mr. Trump later downplayed the Saudi government’s role in the 2018 killing of Jamal Khashoggi, a Saudi dissident journalist, and he defended while in office Saudi Arabia’s long-running military campaign in neighboring Yemen.

After Mr. Trump left office, that relationship continued in the form of a $2 billion commitment by the Public Investment Fund — led by Crown Prince Mohammed bin Salman, Saudi Arabia’s de facto ruler — to an investment fund set up by Jared Kushner, Mr. Trump’s son-in-law. The Saudi fund also put $1 billion into a firm run by Steven Mnuchin, who had been Mr. Trump’s Treasury secretary.

LIV Golf is backed by the same Saudi fund. The head of the fund, Yasir al-Rumayyan, an avid golfer who also took on the role overseeing LIV Golf, spent lavishly to recruit top professional players like Dustin Johnson and Brooks Koepka and big names like Phil Mickelson with $25 million purses and guaranteed contracts that sometimes amounted to $100 million or more.

But the new alliance between the PGA Tour and LIV will also only escalate questions about Mr. Trump and potential conflicts of interest, as he does business with foreign government entities while also running again for the White House.

Already, the Justice Department, as part of its investigation into the handling of classified documents by Mr. Trump, has subpoenaed the Trump Organization, seeking records pertaining to Mr. Trump’s dealings with a LIV Golf.

Under the agreement announced Tuesday, Mr. al-Rumayyan, the governor of Saudi Arabia’s sovereign wealth fund, will join the board of the PGA Tour. Mr. al-Rumayyan also said on Tuesday that the Saudi investment fund is prepared to invest billions of dollars into the merged golf tournament effort.

On Truth Social, Mr. Trump’s social media platform and personal megaphone, he wrote: “Great news from LIV Golf. A big, beautiful, and glamorous deal for the wonderful world of golf.”

Mr. Trump’s son Eric Trump, in an interview on Tuesday, also welcomed the agreement, calling it “a wonderful thing for the game of golf,” adding that he expects tournaments to continue at Trump-owned courses once the merger is complete.

When asked if the Trump family had played a role in urging the PGA Tour and the wealth fund to join forces, Eric Trump declined to comment. But he did say that the family has developed close friends over many years in the golf world, including those associated with the PGA Tour and LIV.

The Trump family has sought to have more of its golf courses host LIV tournaments, including a club in Dubai and the Trump Turnberry golf resort in Scotland, venues it now hopes to see added in future years to a reunified golf industry.

This reflects the intense effort by the Trump family to bring events to its courses, including in Scotland, which the British Open, one of professional golf’s major tournaments, has repeatedly declined to do. While president, Mr. Trump enlisted the American ambassador to Britain to pressure the British government, unsuccessfully, to hold a tournament at Turnberry.

The payments from the LIV tournaments do not show up in Mr. Trump’s financial disclosure report, which he filed in May, suggesting that the fees are going directly to the individual golf clubs and are counted as part of their overall revenues. The Trump family has not said how much they are making from LIV.

“Look, it’s peanuts for me. This is peanuts,” Mr. Trump said in an interview with reporters last month at his golf club in Virginia during a LIV event, adding that “they pay a rental fee. They want to use my properties because they’re the best properties.”

In July, just before the first LIV tournament was played at Trump National Bedminster, Mr. Trump predicted that the rival golf tours would ultimately merge, and he suggested that players who stayed loyal to the PGA Tour were making a financial mistake.

“All of those golfers that remain ‘loyal’ to the very disloyal PGA, in all of its different forms, will pay a big price when the inevitable MERGER with LIV comes, and you get nothing but a big ‘thank you’ from PGA officials who are making Millions of Dollars a year,” Mr. Trump wrote on Truth Social in July 2022. “If you don’t take the money now, you will get nothing after the merger takes place, and only say how smart the original signees were.”

In an interview last year at Trump National Doral, when the LIV tournament was taking place there, Mr. Trump added that he was confident the Saudis were going to win the dispute.

“You’re not going to beat these people,” Mr. Trump said in October. “These people have great spirit, they’re phenomenal people and they have unlimited money — unlimited.”

There won’t be any immediate effect for Mr. Trump, as the PGA and LIV tours at least for now will each continue independently, with the LIV season going forward as planned this year and the PGA sticking to competition sites it had already identified, a spokeswoman for PGA Tour said Tuesday.

But his alliance with the Saudis holds some political risks for Mr. Trump as he campaigns to return to the White House.

The announcement of the LIV-PGA deal immediately generated protests from a group called 9/11 Families United, which has pushed for continued investigation into the origins of the 2001 terror attacks. The group called the efforts by Saudi Arabia to enter professional golf “sportswashing” as part of a plan to improve the country’s reputation related to human rights and allegations that there were links between the hijackers and the Saudi government.

The leaders of the PGA Tour, a spokesman for 9/11 Families United said in a statement, “appear to have become just more paid Saudi shills, taking billions of dollars to cleanse the Saudi reputation,” a claim that also brought demonstrators to Trump National Golf Club in Bedminster last year when the LIV tournament was being played there.

Senator Christopher S. Murphy, Democrat of Connecticut, noted on Tuesday that the PGA had long rejected any talk of merging with LIV.

“PGA officials were in my office just months ago talking about how the Saudis’ human rights record should disqualify them from having a stake in a major American sport,” he wrote on Twitter. “I guess maybe their concerns weren’t really about human rights?”

Alan Blinder contributed reporting.