He was born in Verchères, the son of Jean-Baptiste Chagnon and Marie-Françoise Pinault. Chagnon established himself in business at Verchères. He served as lieutenant in the militia, later reaching the rank of captain. He was married twice: first to Josette Sénécal in 1787 and then to Françoise Dussault in 1813. Chagnon did not run for reelection to the assembly in 1809. He died in Verchères at the age of 59.