"My fantasy is to break up the big banks," the billionaire investor said at the Milken Institute's Global Conference in Los Angeles.
"I wish we would end 'too big to fail' in our banking system but we are not," he said, referring to the idea that certain large, essential financial institutions must be supported no matter what.
Around midday, Trump said in an interview with Bloomberg News that he is considering breaking up Wall Street's giant banks. "I'm looking at that right now," he told the news organization.
Press secretary Sean Spicer added Monday afternoon that the administration is "looking at a 21st-century Glass-Steagall."
Instituted in 1933, the Glass-Steagall Act prevented commercial banks from participating in investment banking. The legislation's partial repeal in 1999 allowed banks to grow into large institutions that ultimately faced massive losses during the financial crisis of 2008.
In order to reduce future risks to the financial system, the Obama administration instituted the Dodd-Frank Act in 2010, which included regulations such as higher capital requirements.
Ahead of his inauguration, Trump had called for repealing Dodd-Frank and breaking up the banks.
— Reuters contributed to this report.