He served as an ensign in the army of New France. After the British gained control of Quebec, he served with the British Army. In 1767, he formed a company to trade with the West Indies. When his father died in 1772, he was the sole beneficiary, inheriting the four seigneuries of Beauport, Fossambault, Gaudarville, and Saint-Roch-des-Aulnaies. From that point on, he spent much of his time administering these properties.
He helped defend the province during the American Revolution and was taken prisoner. His properties were looted during his imprisonment, but he quickly recouped his losses after his release and expanded his property holdings. In 1792, he was elected to the House of Assembly representing Buckingham County and supporting the Parti Canadien. In 1794, he was appointed to the Executive Council of Lower Canada. He died at the Manor house, Beauport, in 1806.
Antoine Juchereau Duchesnay was married twice. In 1765, he married his first wife, Julie-Louise Liénard de Beaujeu de Villemonde (1748–1773), daughter of Louis Liénard de Beaujeu de Villemonde (1716–1802) and niece of Daniel Liénard de Beaujeu. Her mother died when she was young and she was brought up by her father's second wife, Geneviève Le Moyne de Longueuil, granddaughter of Charles le Moyne de Longueuil, 1st Baron de Longueuil. They were the parents of three surviving children,
