"I guess he attended fundraisers, so I take a picture with him. I'm in a room. I take pictures with people. I take thousands and thousands of pictures," Trump said in the Oval Office.
Parnas handed over documents, including numerous images of himself with Trump, members of the Trump family, and high-ranking Republicans, to Democratic lawmakers.
"I don't know him. Perhaps he's a fine man, perhaps he's not. I know nothing about him," Trump said. "I had never had a conversation that I remember with him."
Federal prosecutors charged the Ukrainian-born Parnas and another man, Igor Fruman, with campaign finance violations for trying to conceal large donations to U.S. political groups working to re-elect Trump.
Rudy Giuliani said Parnas helped his efforts in Ukraine aimed at pressuring the government there to announce investigations into unsubstantiated allegations of corruption against one of Donald Trump's Democratic political rivals.
Parnas has offered to cooperate with Democratic lawmakers in their efforts to impeach Trump over the Ukrainian pressure campaign.
In an interview on MSNBC this week Parnas said, "President Trump knew exactly what was going on."
White House spokesperson Stephanie Grisham on Thursday dismissed Parnas's claims, saying "this is a man who’s under indictment and who’s actually out on bail."
She added, "we’re not too concerned about it."