The president made the remarks after the Dow Jones fell by 623 points Friday, a drop sparked by Trump tweets from earlier in the day.
"The global economy has weakened. I think partly it's because of conflicts over trade and the uncertainty that's caused for businesses," Yellen said.
"I want to note in the hearings yesterday with Fed Chairman Jay Powell, it was Ms. AOC asked him about the Phillips Curve," Larry Kudlow told Fox News.
The Fed has often been the target of criticism from the Trump administration, and toward the end of last year, the president had reportedly discussed firing Powell.
Yellen's policies as the Federal Reserve chairwoman helped lower unemployment and spur the country's economic recovery after the 2008 financial crisis, but her legacy will partially depend in part on her successor, Jerome Powell.
Powell is popular within the Federal Reserve system, where he's been a governor since 2012.
'We may be moving more to a more balanced policy with what sounds like more business-friendly regulation and possibly more fiscal support,' Fed governor says.