"Obviously, we feel awful for Kelvin," Panthers general manager Dave Gettleman said in a statement. "He's worked tremendously hard to put himself in a position to have a strong year.
"We're confident he will attack his surgery and rehab with the same determination he has met all challenges before."
Benjamin was taken to Charlotte, North Carolina, for an MRI, which confirmed the tear.
The loss of Benjamin leaves Carolina without its No. 1 wide receiver. Benjamin, who is 6 feet 5, caught 73 passes for 1,008 yards and nine touchdowns during the 2014 season after Carolina selected him with the 28th pick of the draft.
The most likely candidate to replace Benjamin is rookie Devin Funchess, a 6-foot-4, 225-pound receiver selected in the second round out of Michigan in this year's draft.
Funchess suffered a hamstring injury late in Wednesday's practice and is unlikely to be available for Thursday's joint practice.