Alite, Gotti's former best friend, pleaded guilty to two gangland murders and other crimes, the New York Daily News reported.
Federal prosecutors wrote letters to Federal Judge Susan Bucklew praising Alite's cooperation in their prosecution of Gotti as "extraordinary" and "substantial."
"John Alite provided information that materially contributed to the conviction of numerous members and associates of the Gambino organized crime family," Assistant Brooklyn U.S. Attorney Roger Burlingame wrote to the judge.
"People have done a lot more and gotten a lot less," a law enforcement source who worked on the Gotti case told the Daily News.
"It's a very heavy-handed sentence," the source said.
Alite, who has already spent more than six years in prison, could be released in four years because of time served.
Alite began cooperating with federal prosecutors in 2007 after he was extradited from Brazil where he was a fugitive from a gang-related indictment in Florida.