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Louis Eppolito, 57, and Steven Caracappa, 64, now face up to life in prison for their roles in eight murders committed between 1986 and 1990.
At the time they were on the payroll of both the New York police department and Luchese crime family underboss Anthony "Gaspipe" Casso.
Neither defendant showed any emotion during the 10 minutes it took the jury forewoman to reply "proven" 70 times to the charges that included racketeering conspiracy, witness tampering, witness retaliation and obstruction of justice.
The verdict was reached after two days of deliberations.
“Evil personified”
Prosecutors said Eppolito and Caracappa carried out two hits themselves and delivered up some of their other victims to the Mafia to be killed.
Prosecutors said the two used their law enforcement positions to help the Mafia at a price of US$4,000 (A$5,488) per month - more if they personally handled a killing.
In one of the murder cases, the defendants accepted a $65,000 contract from Casso to murder Edward "Eddie" Lino, a Gambino family captain suspected of involvement in an attempt on Casso's life in 1986.
The two shot Mr Lino dead on November 6, 1992 after they pulled him over on Brooklyn's beltway.
The two men "perverted the shield of good and turned it into a sort of evil," US Attorney Roslynn Mauskopf told reporters after the verdict was handed down.
"We gave them that shield. We gave them their power. We trusted them and we expected them to protect us,"
"They didn't deliver us from evil, they themselves were evil personified," Ms Mauskopf added.
Federal prosecutor Daniel Wenner described the case as "the bloodiest, most violent betrayal of the badge this city has ever seen."
Crystal ball
The two officers also supplied Casso with inside information on law enforcement interest in the mob, prosecutors said.
In fact, their information was so useful to Casso that he was said to have referred to the two cops as his "crystal ball."
Caracappa, who retired in 1992, helped establish the NY city police department's unit for Mafia murder investigations.
His attorney, Edward Hayes, had accused prosecutors of compromising Caracappa’s right to a fair trial by leaking pre-trial information about the case to the press.
Eppolito, the son of a Gambino crime family member, was a much-praised street cop, in his autobiography, "Mafia Cop," he portrayed himself as an honest cop from a crooked family.
Eppolito also played a bit part in the mob movie "GoodFellas," after retiring in 1990, he unsuccessfully tried his hand at Hollywood scriptwriting.
No justice
Although the former detectives insisted on their innocence neither took the stand at their trial.
The defendants, who are expected to appeal the verdict, will face sentencing on May the 22nd.
"It's an appearance of justice, but it's not justice," said Bruce Cutler, who once represented the infamous John Gotti and is now representing Eppolito.
Mr Cutler claims the government's mob witnesses were lying to save their necks.