Jacquinot was born in Melun on 3 August 1772. After attending military school at Pont-à-Mousson he joined the 1st Battalion of Meurthe Volunteers as a lieutenant in 1791. He transferred to the 1st Chasseurs à Cheval Regiment as a sous-lieutenant in 1793. Two years later he was appointed aide-de-camp to Pierre de Ruel, marquis de Beurnonville as a lieutenant. During the War of the First Coalition, the 1st Chasseurs fought at the battles of Arlon in 1793, Fleurus in 1794, Altenkirchen in 1796 and Neuwied in 1797. During the War of the Second Coalition the regiment fought at the battles of Ostrach and Stockach in 1799.