In his guilty plea, he agreed to fully cooperate with the federal government. His testimony helped convict his own brother, Frank Calabrese, as well as reputed mob bosses James Marcello and Joey "The Clown" Lombardo.
Family members of some of the victims were outraged at the sentence.
Mob hitman Nick Calabrese knows the inside details of 36 gangland murders. He personally committed 14 of them.
Late on Thursday, a federal judge issued Nick Calabrese his punishment, considering his cooperation and time already served. The most prolific killer in Chicago Outfit history will be out of prison in less than five years.
"I have no faith in the justice system. I really don't. He shot my dad in the head with a shot gun nine times. Did he once apologize to any of the families? No, he did not," said Anthony Ortiz, mob victim's son.
Ortiz' father, Richard, a Cicero bar owner, was murdered by Nick Calabrese in 1983. The Ortiz family was among several that spoke in court Thursday at the sentencing.
There was a parade of victims' loved ones who remember the men who had been tortured and then slaughtered by Nick Calabrese on the orders of Outfit bosses during several decades.
Paul Haggerty was murdered in 1976. On Thursday, his widow, Charlene, looked straight at Nick Calabrese and called him "the devil... diablo. You make me sick to my stomach."
A short time later, Mrs. Haggerty collapsed in a courtroom corridor and had to be taken away by paramedics.
Mobster Nick D'Andrea was killed by Nick Calabrese in 1981. On Thursday, when D'Andrea's son Bob told Calabrese, "Your eternity may be very unpleasant," the hit man's lips began to quiver.
"I see some sorrow in there. Maybe he does feel bad for what he did. All the same, it's not my place to pass judgment or sentence. His day is going to come for that," said Bob D'Andrea. "He's not going to have a comfortable life, whether in jail or on the street."
But when it came time to sentence Nick Calabrese, Judge James Zagel said that if he didn't show leniency to someone who came forward to cooperate with prosecutors and helped to put away a dozen hoodlums and solve so many gangland murders, then future informants might never decide to help in other cases.
"Often the people do not come forward and present evidence, as the judge recognized, unless there is some sort of benefit given for that. And that's what happened in this case," said John Theis, Nick Calabrese's attorney.
"If you do what Nick Calabrese has done, you have the chance of not spending the rest of your life in prison. And in Nick Calabrese's case, he got a break that I'm sure even he didn't expect," said Gary Shapiro, first assistant U.S. attorney.
With his family watching - a daughter in tears - Nick Calabrese told the judge that he had chosen the wrong path in life and was a coward consumed by fear.
Judge Zagel said Nick Calabrese was guilty of terrible crimes but that he has remorse.
Calabrese will be about 70 years old when he is released. But, as Zagel told him, the Outfit "will not forgive or relent in their pursuit of you."
Nick Calabrese is expected to immediately be put into the witness protection program and given a new identity when released.