Not much is known about Tommy DeSimone's early life, but he is remembered as a psychopathic hitman for the Lucchese crime family in New York City. Tommy grew up under the wing of Lucchese capo Paul Vario, who used Tommy to steal trucks and perform other crimes for the family. Tommy was good friends with some of the other famous mobsters under Vario, including Henry Hill and James Burke aka Jimmy the Gent. Tommy told all of his non-connected friends and relatives that he worked as an architecht to explain how he was able to afford so many nice things.

Tommy's brutal and callous nature was well known. His friend, Henry Hill, described Tommy and James Burke by saying, "It didn't take anything for these guys to kill you. They liked it. They would sit around drinking booze and talk about their favorite hits. They enjoyed talking about them."

Once, DeSimone was asked by Burke to take out one of Burke's best friends that had ratted him out. He convinced the man into a car and strangled him with piano wire from the backseat. Another time, Tommy was hanging out in a small bar with his friends and ordered the waiter, a young teenager named Spider, to dance. He then fired his pistol at Spider's feet and hit him in the foot. While Spider was recovering, Tommy started to lace into him again and Spider told Tommy to go fuck himself. The other people in the room laughed about it, but Tommy pulled a gun and shot him three times, killing him.

On another occasion, Tommy went to Robert's Lounge, where a made member of the Gambino Family, Billy Batts, was having a party after being released from prison. Batts was connected with a lot of powerful people and was also a longtime friend of John Gotti. Batts hadn't seen Tommy since he was a kid and shined shoes so he made a comment about his shine box, which really set Tommy off. Tommy told Hill and Burke that he was "going to kill that fuck."

Tommy sent his girlfriend home from the bar and told Burke to keep Billy Batts there while he left to get something. Burke was buying Batts drinks and telling stories when Tommy walked in with a body bag and .38. Tommy came up behind Batts and yelled "shine these fucking shoes" before striking his head with the revolver. They loaded Batts into the car outside and drove to a remote area to bury his body. Along the way, Batts started making noise in the trunk so they pulled over and finished the job with a shovel and tire iron. They finished the trip in Henry's car and dumped the body inside a grave dug inside of a dog kennel.

In 1978, Tommy was scheduled to become a made member of the Lucchese crime family. His friends Burke and Henry weren't full-blooded Italians like Tommy, so they could never become made, making the event very exciting for them. Burke and Henry called from Florida to check up on the event, but Tommy's mother told them that it had been called off. Burke called again the next day, but came out of the phone booth crying because Tommy had been whacked by the Gotti crew for killing Billy Batts and a man named Foxy. Tommy had killed them without getting permission from the Gambino family and violated protocol within the mafia, justifying his execution. It was later learned that Paul Vario had played a role in Tommy's death by setting up the meeting in an effort to avoid trouble with the Gambinos.

On January 14, 1979, Tommy's wife reported that he was missing, but his body was never found. Recently, a mafia grave site was found that is believed to contain Tommy's corpse.

Tommy DeSimone was portrayed by Joe Pesci in Martin Scorsese's "Goodfellas". Joe Pesci won an Oscar for best supporting actor as a result of his amazing portrayal of the infamous mobster.