The pleas came less than two months after the 10-term congressman defiantly said he was the victim of a lynch mob and insisted he would be vindicated of the sexual harassment claims by at least 17 women if due process was allowed to run its course.
His accusers included a retired navy admiral, a university dean and great grandmother.
Filner, however, said little on Tuesday except "guilty" when a judge read the charges against him — one count of felony false imprisonment and two counts of misdemeanor battery.
Under a plea deal, the state attorney general's office will recommend Filner be sentenced to three months of home confinement and three years of probation. The maximum possible sentence for a false imprisonment count is three years in prison and one year for each count of battery.
Filner restrained a woman against her will at a fundraiser on March 6, applying additional force after she resisted, according to the plea agreement. Filner put her in a headlock, his attorney, Jerry Coughlan, told reporters.
He also kissed a woman without permission at a "Meet the Mayor" event on April 6 and groped another victim at a May 25 rally to clean up Fiesta Island in Mission Bay. None of the victims were identified.
Filner, 71, did not comment after the hearing but his attorney said the former mayor "profusely apologizes" for his behavior.
"I think he wants to redeem his original legacy, which was a wonderful one, and put this behind him," Coughlan said. "He's been jogging, he's been getting therapy, talking to friends, trying to come to terms with how to deal with these kinds of problems. It's a full-time job."
Filner resigned Aug. 30, succumbing to intense pressure after the parade of women accused him of sexual harassment. He had held the office for less than nine months of a four-year term and was San Diego's first Democratic mayor in 20 years.
The San Diego County Sheriff's Department opened a hotline for complaints about Filner in July and said it would deliver findings to the attorney general's office for possible prosecution. The state attorney general's office later confirmed that it launched a criminal investigation.
"This conduct was not only criminal, it was also an extreme abuse of power," California Attorney General Kamala Harris said. "This prosecution is about consequence and accountability. No one is above the law."
Filner's attorney said prosecutors were eager to strike a deal before a grand jury began hearing testimony about Filner's behavior. The grand jury probe will no longer go forward.
The criminal charges do not involve Filner's former communications director, Irene McCormack Jackson, who was the first to go public with sexual harassment allegations in July. She has filed a lawsuit against the mayor and the city, claiming her ex-boss asked her to work without panties, demanded kisses, told her he wanted to see her naked and dragged her in a headlock while whispering in her ear.
In exchange for Filner's resignation, the city agreed to pay his legal fees in a joint defense of the McCormack Jackson lawsuit, and to cover any settlement costs assessed against the mayor, except punitive damages. The city did not represent him in the criminal case.
Gloria Allred, an attorney for McCormack Jackson, applauded the outcome of the criminal case and the women who came forward to share their stories with investigators.
"It is long overdue for him to be accountable in both the civil and criminal justice system and today is an important step forward in bringing Bob Filner to justice," she said.
As a convicted felon, Filner forfeits his right to vote. In addition, his pension will not accrue from the time of the first offense in March, Coughlan said.
Mike Aguirre, a former San Diego city attorney who is running in a Nov. 19 special election to replace Filner, said the felony plea marked an astonishing fall for the former mayor.
"As a lawyer, when I see someone plead guilty to a felony, that is an indelible mark. That is a scarlet letter that will always be emblazoned on his chest. He will never be able to erase it," Aguirre said.
Filner spent two months in a Mississippi jail for inciting a riot when he joined the Freedom Riders in 1961 to campaign against segregation. He often cited that experience during his long political career that included stints on the San Diego school board and City Council and in Congress.
He became a political pariah before stepping down. All nine City Council members and the Democratic National Committee called upon Filner to resign. A recall effort also was launched as allegations surfaced.