Donald Trump's eldest son, son-in-law and campaign chairman met a Russian lawyer shortly after the tycoon won the Republican nomination.
It appears to be the earliest known private meeting between key aides to the president and a Russian.
Representatives of Donald Trump Jr and Jared Kushner confirmed the June 2016 meeting to The Associated Press after The New York Times reported on Saturday on the gathering of the men and Russian lawyer Natalia Veselnitskaya at Trump Tower.
Then-campaign chairman Paul Manafort also attended, according to a statement from Donald Trump Jr.
He described it as a "short introductory meeting" during which the three discussed a disbanded programme that used to allow US citizens to adopt Russian children.
Russia ended the adoptions in response to American sanctions brought against the nation following the 2009 death of an imprisoned lawyer who spoke about a corruption scandal.
Mr Trump Jr said he invited the other two Americans, was asked to attend by an acquaintance not named in the statement, and was not told beforehand with whom he would meet.
"It was not a campaign issue at that time and there was no follow up," he said.
Kushner lawyer Jamie Gorelick said her client already disclosed the meeting in a revised filing of a form that requires him to list contacts with foreign agents.
She said: "Mr Kushner has submitted additional updates and included, out of an abundance of caution, this meeting with a Russian person, which he briefly attended at the request of his brother-in-law, Donald Trump Jr.
"As Mr Kushner has consistently stated, he is eager to co-operate and share what he knows."
Later on Saturday, a spokesman for the president's outside legal team contended that participants in the June meeting "misrepresented who they were and who they worked for".
However, the spokesman, Mark Corallo, would not say specifically who misrepresented themselves or how they did so.
Unlike Mr Kushner, Mr Trump Jr does not serve in the administration and is not required to disclose his foreign contacts.
The newspaper reported on Saturday, citing unnamed people familiar with the matter, that Mr Manafort disclosed the meeting to congressional investigators questioning his foreign contacts.
Mr Manafort ran Mr Trump's campaign for about five months until August and resigned from the campaign immediately after the AP reported on his firm's covert Washington lobbying operation on behalf of Ukraine's ruling political party.
He is one of several people linked to the Trump campaign who are under scrutiny by a special counsel and congressional committees investigating Russian meddling in the 2016 campaign and potential co-ordination with Trump associates.
Mr Manafort has denied any co-ordination with Russia and has said his work in Ukraine was not related to the campaign.
The newspaper said Ms Veselnitskaya is known for her attempts to undercut the sanctions against Russian human rights abusers.
It also said her clients include state-owned businesses and the son of a senior government official whose company was under investigation in the United States at the time of the meeting.