He served as lieutenant in the Royal Canadian Volunteer Regiment from 1798 to 1802.
Juchereau Duchesnay was elected to the Legislative Assembly of Lower Canada for Hampshire in 1804; he represented the county until 1810 when he was named to the Legislative Council.
He inherited the seigneury of Beauport from his father in 1806.
In 1809, he became assistant to the adjutant general for the Lower Canada militia.
He was named justice of the peace in 1813 and commander of the Beauport militia in 1816.
In 1817, he was named to the Executive Council; he had been an honorary member since 1812.
In 1821, Juchereau Duchesnay was named to the board of trustees for the Royal Institution for the Advancement of Learning.