"I think the weight of the evidence and of what's happened leads to that conclusion," Nadler said.
Nadler's comments came after the Justice Department confirmed that Barr would voluntarily testify before his committee next month.
They were a marked departure from only days earlier, when Nadler said he viewed impeachment as a "waste of time.".
"I don't think calls for his impeachment are premature any more than calls for the president's impeachment were premature," Nadler told CNN on Sunday.
Barr also fired U.S. Attorney Geoffrey Berman, who was investigating Trump attorney Rudy Giuliani and others in the president's orbit.
And momentum could be shifting, with at least two Democrats publicly calling for impeachment on the day of the whistleblower testimony.
"We should pursue impeachment of Bill Barr, because he is reigning terror on the rule of law," Cohen said. »