"I think it is terrible. I think Gary is a very strong proponent of economic growth and is quite bright and knowledgeable," Dimon said in an interview with Bloomberg TV. "I think he was good to have in the White House, not as the press writes to defend Wall Street. He knows how an economy runs, he knows what needs to be done to make it healthier for all Americans, and he's not there. It's unfortunate."
Cohn, a former Goldman Sachs president, resigned Tuesday after losing his fight against stiff tariffs on steel and aluminum.
Dimon's remarks on Cohn are a bit stronger than what Goldman Sachs CEO Lloyd Blankfein said on Tuesday.
"Gary Cohn deserves credit for serving his country in a first-class way. I'm sure I join many others who are disappointed to see him leave," Blankfein said in a Tweet.
Dimon also criticized President Donald Trump's plan for a 25 percent tariff on steel and 10 percent on aluminum.
"I think tariff is the wrong way to go about it. Of course there may be more, there may be retaliation, it kind of opens up the whole Pandora's Box of additional problems," Dimon told Bloomberg. "If it continues and it gets worse, yes it will hurt growth. … It could offset some of the huge positive we had from competitive tax reform."