Cosby, 81, was also categorised as a sexually violent predator, meaning he must undergo counselling for life and be listed on the sex offender registry.
The actor declined to make a statement when offered the opportunity.
At a retrial in April, Cosby was found guilty of three counts of sexual assault for drugging and molesting Andrea Constand in 2004.
Cosby's request for bail pending appeal was denied. He was also fined $25,000 (£19,000) plus the prosecution costs.
After the sentencing, he was led away in handcuffs from the courtroom. He was then driven to Montgomery County Correctional Facility.
Cosby's attorney had asked for his sentence to be restricted to house arrest, saying he was too frail for prison.
The actor had been under house arrest since April.