"I think they'll have a substantial impact on the economy," Schwarzman told "Squawk Box" from the World Economic Forum in Davos, Switzerland.
Schwarzman, who led the president's policy forum before it was disbanded, said Trump can take credit for the improved confidence of business leaders and the roaring stock market.
"You started to see this right after the election, and the stock market started going up just in the anticipation of tax reform and tax cuts and changes in regulation," Schwarzman said. "Those things happened and are happening."
Since the election, the Dow Jones industrial average has gained more than 42 percent as of Monday's close; the has gained more than 32 percent; the is up more than 42 percent.
Trump has repeatedly taken credit for the U.S. stock market's record run.
Schwarzman had Trump's ear as chairman of the president's Strategic and Policy Forum, a group of influential American CEOs that was set up to periodically to give Trump advice.
The group disbanded last summer as CEOs revolted against Trump's equivocal comments about white supremacist violence at a rally in Charlottesville, Virginia.
Trump is expected to speak at Davos later this week, touting his "America First" message.
Schwarzman, co-founder of private equity giant Blackstone, said he'd been told the president's speech is "pretty good" adding whatever Trump says will be heavily "considered."