Bennett was tested Monday and placed in isolation after showing symptoms of the disease, general manager Jim Rutherford said. The team confirmed the diagnosis Tuesday after a series of tests.
The 23-year-old Bennett also was one of the Penguins players to visit the Children's Hospital of Pittsburgh last week. The hospital released a statement Monday that said children who have not received an age appropriate vaccine and who were in contact with Bennett will be put in isolation and monitored for symptoms.
"They're testing any possible people he may have come in contact with, and they're on top of the situation," Rutherford said Monday. "We feel bad about that."
Bennett was already out indefinitely while dealing with a lower-body injury. It's uncertain when he will be cleared to rejoin the club.
The Penguins have aggressively tried to prevent the disease from spreading by having players and staff undergo testing this month.
Rutherford said Crosby is past the infectious stage and could return to the team later this week.
Bennett becomes the 12th player around the league to have contracted the disease, which is usually found in children, and its symptoms include facial swelling and fatigue. Players from the Anaheim Ducks, Minnesota Wild, New Jersey Devils and New York Rangers have been affected.
In light of the mumps situation, the league sent out a memo in conjunction with the NHL's Infection Control Subcommittee last month to provide clubs' medical personnel and trainers with recommended guidelines and protocols to assist in both the treatment and prevention of the disease.
Dr. Greg Wallace, a lead epidemiologist at the Centers for Disease Control and Prevention in Atlanta, told ESPN.com that considering the lengthy incubation period of the mumps, it's virtually impossible to predict how long this outbreak will affect the league.
The CDC receives anywhere from a couple hundred to a couple thousand reported cases of mumps annually.
Katie Strang of ESPN.com and The Associated Press contributed to this report.