The disgraced comedian and actor, 83, said he wouldn’t acknowledge wrongdoing in the programme even if it meant serving his full 10-year sentence.
This is the first year he was eligible for parole having served three years in state prison in Pennsylvania.
Cosby spokesman Andrew Wyatt called the decision “appalling” and his client “vehemently proclaims his innocence”.
He added: “We knew he was going to be rejected. He called me and told me that if he didn’t take the course, he would be denied. He has maintained his innocence from the beginning.”
The fallen star meanwhile hopes the state Supreme Court, which heard his appeal in December, will reverse his 2018 conviction in the first celebrity trial of the #MeToo era.
Cosby's lawyers say the trial was flawed because five other accusers were allowed to give evidence to support the sexual assault complaint filed by a former Temple University basketball team manager.
They also say the judge should not have let the jury hear Cosby's damaging evidence from accuser Andrea Constand’s related civil suit.
Cosby is serving his sentence at SCI-Phoenix in Montgomery County for drugging and sexually assaulting Ms Constand at his estate near Philadelphia in 2004.
The two had met at Temple where Cosby long served on the board of trustees and was a frequent celebrity visitor to campus.
Ms Constand has granted permission to be identified in media reports.
In the wake of the decision, she posted a tweet that said simply: “Denied”.
Laura Treaster, a spokesperson for the Pennsylvania parole board, said in a statement that Cosby would not be considered for parole until he completes the sexual violent predator therapy.
Officials will interview Cosby again after they’ve “been notified that he has completed his programming,” she said.
Cosby broke racial barriers in Hollywood in the 1960s.
He was once a towering figure in the entertainment industry known as “America’s dad” for his role as head of the Huxtable household on The Cosby Show sitcom from 1986.