The photograph, posted Wednesday on Reddit, became the latest showing bad behavior at a fast-food restaurant to go viral, The New York Daily News reported.
It joins other Internet classics like the Taco Bell employee who was fired for licking taco shells.
Wendy's spokesman Bob Bertini, in an e-mail to the News, was coy about when the incident happened and which restaurant was involved. The photo shows an employee sucking soft ice cream directly from the dispensing machine.
Bertini said the employee is no longer with the restaurant.
"We don't know the exact date the photo was taken, but we believe in it was in May," Bertini told the News. "The incident was totally inappropriate, and we're taking it very seriously."