Diamond was elected Chief of the Cree Nation of Waskaganish at the age of 21.[5][2] On November 11, 1975, he signed The James Bay and Northern Quebec Agreement with the Canadian government.[6] Using funds from the settlement, he created Air Creebec, Cree Construction Company Limited, and Cree Yamaha Motors.[4] For his outstanding achievements, Billy Diamond was appointed as a Chevalier into the Ordre National du Quebec in 1987.[7] On March 19, 1990, Diamond was a guest on 100 Huntley Street.[8]
Diamond died at the age of 61 from a heart attack. In accordance with his instructions, his tombstone reads: "Gone to a meeting - will return."[9]