Renita Hill, 48, a Pittsburgh resident, in October filed the lawsuit for three separate comments made by Cosby and his representatives after she spoke publicly of alleged sexual misconduct in the 1980s.
"The three statements do not support a claim for defamation as defined by Pennsylvania law," U.S. District Judge Arthur Schwab said in his dismissal ruling, court documents showed.
Cosby mentored Hill when she was a young woman in the 1980s and paid for her education at Temple University and Spelman College, her attorneys have said. They said Cosby arranged meetings with Hill in Atlantic City, New York City and Denver, where he sexually assaulted her.
Hill first publicly claimed Cosby sexually assaulted her in an interview with a local Pittsburgh TV station in 2014. She said she had been emboldened by other women who had come forward. Cosby and his representatives responded in three separate statements by depicting Hill as a liar and an extortionist who was out for money, her attorneys said.
Schwab said the remarks by Cosby and his team were protected under their right free speech. He also said Hill could not prove the comments inflicted harm upon her. Hill is one of more than 50 women who have come forward to accuse Cosby, 78, of sexual assault dating back to the 1960s.
Hill's suit, filed in Pittsburgh, was one of several against Cosby by women whose accusations date back decades. Due to statutes of limitations, many of the allegations are too old to be the subject of criminal charges. Still, they have toppled Cosby from his cultural status as one of America's most-admired comedians.
Cosby built his career on family-friendly humor and was best known for his role as the dad Heathcliff Huxtable in the long-running 1980s television hit, "The Cosby Show."
The only criminal charges against Cosby were filed last month for the alleged sexual assault of Andrea Constand in 2004 in the actor's Philadelphia-area mansion. Cosby, who has repeatedly denied wrongdoing, is free on $1 million bail. His lawyer has said he is not guilty and will not consider a plea bargain.