The son of a merchant in Bordeaux, he was sent to Nantes to learn his trade but there became interested in politics and philosophy, joining several such circles, in which he gained a reputation for patriotism.
There he sat with the Girondins (but tended to favour the opinions of the Montagnards) and took up marked positions, such as in the issues surrounding Louis XVI, the abolition of the monarchy and the question of the refractory priests.
Protection from Marat meant he escaped a purge on 2 June 1793, but he fell under suspicion due to his protests against the arrests and summary 'disappearances'.
He was guillotined on 31 October alongside other Girondins, including his friend and brother-in-law Jean-Baptiste Boyer-Fonfrède.
Noted for his caustic wit, Ducos reputedly remarked, while awaiting his turn at the guillotine, "The Convention has forgotten one thing: a decree on the unity and indivisibility of heads and bodies."