- "I was just doing what Uncle Sal told me to do..."
- — Michael Grecco
Michael's childhood was tough; his mother abandoned him and his father, Michael Sr., when he was only 3 years old. A few years later, Michael Sr. married Sal's sister-in-law. After the wedding Michael, Sr. started selling dope for Lou Marcano. This went on for a few years until he got arrested, looking at ten years unless he testifies. The day after he agreed to turn on the Marcanos, he was found dead, neck broken in three places from an apparent "suicide".
Working for Marcano
Sal refused to abandon his sister, so he took care of her and Michael. Once he was older, his mother started angling to get him work in the family business, and Sal was happy to oblige. To Sal, it looked like Michael was climbing the ladder, but according to some of the old-timers, the only thing Michael's good at is failing upwards. He tends to come in, stir things up, and then blame it all on someone else when it blows up in his face. 
Taking River Row
Sal's wanted to get rid of Vito Scaletta for years, as he figures he's a mole for The Commission, but he can't do anything about it because Vito's a Made Man. After the heist, Sal refuses to give Vito his cut, and then puts Grecco in charge of River Row to "help" Vito run things. The goal is to restrict Vito's ability to kick up, and when he can't pay, the Commission will give Marcano permission to whack him.
After taking over River Row, Grecco uses his men to limit what Vito can do. Roy Thibideaux is placed in charge of the contraband racket and Andy Turetto, who was running the dockworkers union for Vito, is now getting his orders from Grecco. This cuts off Vito's ability to earn, and with him boxed in, Grecco makes his move. They lock Vito in the freezer of his restaurant while they try to find out what other rackets he is running. This plan is foiled when Lincoln Clay arrives and takes out Grecco's men to save Vito.
Downfall and Death
After taking over his contraband and extortion rackets, Lincoln and Vito make their move on Grecco. They've learned he's currently holed up with a bunch of whores in a run-down shack, but as they're about to move in, a group of Marcano's men arrive to take Grecco out themselves, forcing him to flee. Determined to kill Grecco himself, Vito insists they chase after him.
After dealing with Marcano's men, the two bring Grecco back to Vito's place for questioning. They learn that the real reason Sal wants Vito dead is because he's afraid Vito knows about the casino and plans to tell Leo Galante and the Commission about it. He goes on to explain that the construction across the lake is Sal's new casino. He plans to go legit and turn New Bordeaux into the next Las Vegas after he bribes enough politicians to get gambling legalized. After telling them this, Grecco asks if they will let him go now, but he's knocked unconscious instead. Lincoln leaves him with Vito, who presumably grinds him into chum and feeds him to the fish.
- Michael Grecco, Sr. (father, deceased)
- Sal Marcano (uncle, deceased)
- Giorgi Marcano (cousin, deceased)
- Fish Gotta Eat (killed)
- Michael's dossier unlocks after completing "We Partners Now?" in Work the Man Who Bleeds.