"Ackman is completely and totally wrong on this company" Icahn said in an interview with CNBC's "Squawk Box" Thursday. "Ackman is a smart guy and all but he's just dead wrong. This company creates work for a lot of people and to say that it doesn't is ridiculous."
Ackman, head of Pershing Square Capital Management, claims Herbalife is a pyramid scheme. He first shorted the company in 2012.
The two billionaires had an unforgettable battle on CNBC in January 2013 over the nutritional supplement company. The two traded insults, with Icahn calling Ackman a "liar" and a "crybaby."
The pair mended fences a year later.
"We made up. We talk to each other so I'm not going to say anything bad about him except I disagree with him," Icahn said Thursday.
A spokesperson for Pershing Square Capital Management declined to comment.