"Nonsense," said the International Federation of Associated Wrestling Styles, headquartered in Switzerland.
The group says it represents wrestlers from 180 countries, including many where wrestling is the national sport and the only sport that gives athletes a route to participation in the Games.
Federation officials will meet this week in Thailand to discuss the IOC's decision and how to make a case for wrestling at the May IOC Executive Board meeting.
Meanwhile, on the message boards of TheMat.com, the official website of USA Wrestling, posters were calling the IOC decision the death of the sport in the U.S.
"You know what this means it is dead. What reasons do universities now have to keep programs that are not revenue sports that are not Olympic Sports," wrote one.
"The day of reckoning has arrived for our beautiful sport. What a sad, sad course of events," wrote another.
But at least one poster saw some logic in the IOC's popularity reasoning and pointed at mixed martial arts, the combination of boxing, wrestling and martial arts that is drawing legions of new fans.
"It's time to join forces with mma, because of its growing world wide popularity, and secure our growth and future as an essential part of its makeup. If we do not make this connection, we present ourselves as a single, fringe sport on the outside of popular" culture, one poster wrote.
The host city for the 2020 Summer Games will be chosen in September. Istanbul, Tokyo and Madrid are the finalists.