Petraeus is a former commander in Iraq and Afghanistan, and a former CIA director. He resigned in 2012 after revelation of his extramarital affair.
The Hill newspaper said Petraeus spoke at the Institute for National Security Studies in Tel Aviv.
"At the end of the day the damage done [by Snowden] is enormous," Petraeus was quoted as saying by a Jerusalem Post reporter who tweeted from the event.
Snowden is a former National Security Agency contractor who fled abroad. Now protected by temporary asylum in Russia, Snowden released details of the NSA's massive intelligence collection program.
Petraeus said Snowden did "the most damage of any spy, turncoat, whatever," the New York Times' Jerusalem bureau chief tweeted.
Petraeus last year was appointed a visiting professor at CUNY's Macaulay Honors College in New York.
Notable deaths of 2014 [PHOTOS]
Rebel rocket attack kills 10 in Ukraine