Japan's PM Shinzo Abe has said he has "great confidence" in US President-elect Donald Trump and he believes they can build a relationship of trust.
Mr Abe described the 90-minute meeting in Trump Tower, New York, as "candid", with a "warm atmosphere".
Some of Mr Trump's campaign rhetoric cast doubt over long-standing US alliances, including with Japan.
The meeting was Mr Trump's first face-to-face with a world leader since winning the presidential election.
The US and Japan have been key allies since the end of World War Two, when the US helped Japan rebuild its economy.
The president-elect has vowed to scrap the Trans-Pacific Partnership trade deal, which Mr Abe strenuously supports as a means of countering China's growing economic strength.
The deal was approved by the Japanese parliament, despite the likelihood that the deal will be cancelled when Mr Trump takes office.
The two men met at Trump Tower in New York
Mr Trump has also said Japan needs to pay more to maintain US troops on its soil, and has floated the idea that Japan and South Korea should develop their own nuclear weapons to counter the threat from North Korean missiles.
The meeting was reportedly arranged when Mr Abe rang the president-elect to congratulate him, mentioning that he would be passing through New York on the way to an Asia-Pacific trade summit in Peru.
Speaking after the meeting, Mr Abe said: "We were able to have a very candid talk over a substantial amount of time. We held it in a very warm atmosphere.
"I do believe that without confidence between the two nations the alliance would never function in the future and as the outcome of today's discussion I am convinced Mr Trump is a leader in whom I can have great confidence in."