In an interview with One America News, the former president revealed he had been swayed to support Dr Oz in the Republican primary due to flattering remarks.
“I know Oz for a long time and he’s been very nice to me over the years,” Mr Trump said.
“And that, you know, influences you in all fairness. I’ve really liked him. I’ve been on his show.
“He always treated me well. He said I’m a very healthy specimen which I liked very much. He said ‘if you lost a couple of pounds that would be OK too’, but that’s alright.”
Mr Trump’s endorsement of the Turkish-American heart surgeon sealed his narrow win over former hedge fund chief executive David McCormick by a margin of less than 1,000 votes in last month’s primary.
Dr Oz will face Democrat John Fetterman in the general election in November.
Mr Fetterman has relentlessly attacked Dr Oz for his loose ties to Pennsylvania on social media since winning the Democratic nomination in a landslide, mocking the veteran television host as an out-of-touch carpetbagger.
Dr Oz first appeared on The Oprah Winfrey Show in 2004 as a guest medical expert before hosting his own television show for 13 seasons.