"I like what this administration is doing by being ... trying new ideas" on trade, O'Leary said on "Fast Money Halftime Report." "Because to me it's starting to work."
O'Leary, often referred to as 'Mr. Wonderful' on "Shark Tank," made the comment in response to tweets from the president earlier Tuesday.
Trump complimented the "Shark Tank" investor and "Mad Money" host Jim Cramer, who has also been generally supportive of the White House approach to China.
As shown in the tweet, O'Leary said on CNBC that "I'm really tired of the last 15 years. Finally an administration that's batting for the guy that puts his capital up there and gets screwed over and over again."
In response to O'Leary, Cramer said, "I'm listening to Mr. Wonderful and I think Mr. Wonderful is dead right on everything because it's factual. It's empirical and thank you for speaking the truth."
He also added, "This is the strongest I've ever seen in the economy and it's also an unbelievable moment in terms of inflation. It's just not there. Why do we need the Chinese at all?"
The U.S. Treasury Department on Monday designated China a currency manipulator, a move that has not been seen since the Clinton administration. U.S. stocks had been selling off since Trump announced last week he would impose new tariffs on Chinese goods.
China, which has historically controlled its currency, allowed the yuan to fall to its lowest level in more than a decade earlier Monday. The Chinese currency has not broke over the 7 level against the dollar since the global financial crisis in 2008.
After the currency move, U.S. stocks plunged Monday. The market recovered some of the lost ground on Tuesday after China set a path for the yuan to strengthen.
Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."