In an interview with NBC's Today show, the 59-year-old revealed he was diagnosed in September 2018 after a routine physical examination.
The cancer has since spread to the actor's bones and he can no longer walk. He is undergoing chemotherapy.
"Eventually, you know, it's gonna probably get me," he told host Craig Melvin.
Speaking about his diagnosis, he said: "I was 56 years old at the time, and they screen for PSA, which is prostate-specific antigen.