Martorano is the younger brother of notorious "hitman" and later government witness, John Martorano. James Martorano was born in Somerville, Massachusetts. His father, Patriarca crime family associate Luigi Martorano, was an immigrant from Emilia-Romagna, Italy. His Irish-American mother was a full time homemaker. The Martorano family soon moved to East Milton, Massachusetts. He went on to attend Mount Saint Charles Academy with his brother John, in Woonsocket, Rhode Island.