As then-president-elect Trump sat on a mini-throne during the interview, the painting could be seen hanging on a wall in the background, where the masterpiece looks out of place, except for its gold frame.
Trump's biographer, Tim O'Brien, was familiar with the painting as he grew up in Chicago.
The Chicago Institute of Art has issued a statement pointing out that the 1881 painting by French artist Pierre-Auguste Renoir, titled "Two Sisters (On the Terrace)", hanging at Trump's NY property, is a copy.
The next time O'Brien saw Trump's allegedly fake Renoir was after the 2016 presidential election, when Trump was interviewed on "60 Minutes". "I asked him about the painting and Donald said, "It's a (n) original Renoir.' And I said, 'No, it's not, Donald", he recalled in a Vanity Fair podcast. Trump said it was.
In 2006, Trump sued O'Brien, author of "TrumpNation: The Art of Being the Donald", for writing in his book that Trump's net worth was $150 million to $250 million.
However, O'Brien replied: "Donald, it's not".
The following day, Trump appeared to have forgotten the previous day's conversation, and declared: "You know, that's an original Renoir".
Art Institute spokeswoman Amanda Hicks said the institute is "satisfied that our version is real". He does not bother mincing his words when talking about the president and opined that Trump probably "believes his own lies".
CLARIFICATION: This headline has been updated to clarify the Chicago Art Institute's comment that they own the original Renoir.
O'Brien said: "I'm sure he's still telling people who come into the apartment, 'It's an original, it's an original'".
Mr O'Brien told Vanity Fair's "Inside the Hive" podcast that he alerted the US President to that fact that the painting was a fake.
The donor acquired it for $100,000 (£760,000) from an art dealer who bought it directly from the French Impressionist painter in 1881, she added.