He went behind bars as inmate No. 84888-054 at the Cumberland Federal Correctional Institution in Cumberland, Md., said Felicia Ponce, spokeswoman for the Bureau of Prisons. She said Kerik, 54, reported at about 1:45 p.m., 15 minutes ahead of his deadline.
Before showing up at the prison, the feisty former commissioner issued a statement saying he had been wronged.
In a statement dated Sunday and posted on his website, Kerik said he could not remain silent "in the face of what I believe has been a grave injustice." He complained about the judge and prosecutors and said he pleaded guilty because he was "financially helpless" and could have spent a year behind bars just awaiting trial.
He said he hoped the "injustice" would be remedied on appeal and he would be returned to his wife and his 7- and 10-year-old daughters "much sooner rather than later."
Kerik's steely resolve as he stood with his mentor, Mayor Rudolph Giuliani, after the 9/11 attacks won him worldwide fame. His career peaked three years later when he was nominated by President George W. Bush to lead the Department of Homeland Security.
While he was being vetted, however, questions were raised about his finances and associations, and he bowed out of the nomination. He later admitted in court that he lied when he denied having any financial dealings with anyone doing business with New York City.
Kerik pleaded guilty in November to eight felonies. When he was sentenced in February, White Plains federal Judge Stephen Robinson said Kerik had used 9/11 "for personal gain and aggrandizement." The judge went beyond federal sentencing guidelines, which suggested two to three years in prison, because of what he called "the almost operatic proportions of this case."
After his sentencing, Kerik apologized to the nation and said he hoped history would take into account the "30 years of service I've given to the country and the city of New York."
In a television interview last month, Kerik said he stopped speaking with Giuliani in 2006, as the former mayor began running for president, to protect him. He added, however, "We will be friends for life."
Kerik said on his website that he recently watched the movie "Rocky Balboa" with his daughters to illustrate "the principles of courage, strength and perseverance" in anticipation of his imprisonment.
He said he told the girls, "It is time to move forward."
Ponce said Kerik would have his photo and fingerprints taken, undergo physical and psychological exams and be assigned to a housing unit at the 1,500-inmate prison.