Zack Sinclair, who had confronted Gibson after the release of the actor-director's film "The Passion of the Christ," was convicted in March of one felony count of stalking.
Sinclair was arrested in September 2004. Prosecutors said he went to the gate of Gibson's Malibu estate repeatedly that month after evading neighborhood security and asked to pray with the star.
The 35-year-old Sinclair, dressed in a yellow and blue jail jumpsuit, acted as his own lawyer. He declined to speak during the brief sentencing hearing in Superior Court.
He has remained in custody and will immediately begin serving the sentence.
Gibson, 49, wasn't in court for the sentencing. A message left for his spokesman wasn't immediately returned.
During the trial, Gibson testified that he was attending church services in September when he got up briefly and returned to find Sinclair sitting in his seat. Sinclair moved within a few inches of his face, Gibson said, telling him, "Hi, I'm here to pray with you."
Gibson said Sinclair wasn't "overtly threatening," but he worried about his family's safety.
"My wife was upset and worried. She didn't want to find him in the living room drinking tea," Gibson said.