The president has been treating the central bank like a "pinata," Cramer said on "Squawk on the Street." But Powell "ain't quittin'. ... This is a guy who is doing his job. He's adjusted to doing his job."
Cramer spoke after the Wall Street Journal reported that former Fed officials and foreign central bankers worry that Trump's combative stance toward the U.S. central bank could weaken the institution. They say the president's approach could erode nonpartisanship in the Fed's boardroom over time, according to the Journal.
Trump has blamed the Fed's policies, particularly on interest rates, for previous declines in the stock market and slow economic growth.
On Sunday, the president renewed his attack on the central bank in a tweet, saying, "If the Fed had done its job properly, which it has not, the Stock Market would have been up 5000 to 10,000 additional points, and GDP would have been well over 4% instead of 3%."
Cramer said he expects Trump may have "got the wrong guy" when he chose Powell to lead the Fed. But the president shouldn't expect Powell to respond to his criticisms now.
Trump nominated Powell in November 2017 to succeeded Janet Yellen as central bank chair. Powell has been a member of the Fed's board of governors since 2012.
Cramer has also been critical of Powell since the Fed chairman's remarks on Oct. 3 that the cost of borrowing money was a long way from so-called neutral, sparking concerns about possibly more aggressive Fed tightening.
But Cramer expressed renewed optimism about Powell's leadership in March when the central bank indicated it would stall interest rate increases for the year.
"I thought that Jay was great," Cramer said at the time. "It's not easy to start. You make your rookie mistakes, you come back. He's a great guy. Anyone who knows him knows that he course corrected."