Disgraced former New York Congressman Anthony Weiner is now behind bars.

Weiner surrendered to authorities at Devens Federal Medical Center in Massachusetts on Monday.

He sobbed in court in September when the judge sentenced him to 21 months for sexting a 15-year-old girl.

The politician was also hit with a $10,000 fine.

Once released, Weiner will have to check into a sex offender treatment program.

He pleaded guilty back in May to charges of sending lewd material to the teenager in North Carolina.

No stranger to sex scandals, this conviction ended Weiner's marriage to former Hillary Clinton aide Huma Abedin after having a big impact on last year's presidential election. The FBI used emails found on his laptop to justify reopening the Clinton private server investigation.

Weiner has joined about 1,100 inmates at the prison, which is one of nine that offers sex offender treatment programs.

Weiner is expected to undergo group and one-on-one counseling. With good behavior, he could leave custody months early.

"If he does everything he's supposed to do in prison and does not get himself into any trouble in prison, then he'll receive 54 days off for each year that he's sentenced," said Dominic Saraceno, a criminal defense attorney who specializes in sexual offenses.

Saraceno also said that toward the end of the sentence, Weiner will have to register as a sex offender, which has three levels.

Saraceno predicts Weiner will receive the least restrictive classification. "Because he has probably no criminal history, other than this instance offense. He will likely comply with his treatment while he's incarcerated," the defense attorney said.

That would still mean Weiner would be in an online database and required to alert police of his address yearly for 20 years.