"Donald is 180 degrees wrong," Cuban told CNBC's "Squawk Alley" by phone.
In a Reuters interview, Trump said technology start-ups that had never earned a profit were able to sell shares at very high price. He likened the situation to the overheated stock market in 2007.
"I'm talking about companies that have never made any money, that have a bad concept and that are valued at billions of dollars, so here we go again," the New York tycoon told Reuters.
Cuban, a tech entrepreneur and owner of the Dallas Mavericks, said Trump's comments make it sound like there's a bubble in the public markets, which isn't true.
"That's 180 degrees wrong because none of those companies are going public," the "Shark Tank" host said.