His father, who was an architect, died when Sedaine was quite young, leaving no fortune, and the boy began life as a mason's labourer. He was at last taken as pupil by an architect whose kindness he eventually repaid by the help he was able to give to his benefactor's grandson, the painter David.
Meanwhile he had done his best to repair his deficiencies of education, and in 1750 he published a Recueil de pièces fugitives, which included fables, songs and pastorals. His especial talent was, however, for light opera. He produced Le Diable à quatre (1756), the music being by several composers; Blaise le Savetier (1759), for the music of Danican Philidor; On ne s'avise jamais de tout (1761) and others with Pierre-Alexandre Monsigny; Aucassin et Nicolette (1780), Richard Coeur-de-lion (1784), and Amphitryon (1788) with André Grétry.
Sedaine's vaudevilles and operettas attracted the attention of Diderot, and two plays of his were accepted and performed at the Théâtre Français. The first and longest, the Philosophe sans le savoir, was acted in 1765; the second, a lively one-act piece, La Gageure imprévue in 1768. These two at once took their place as stock pieces and are still ranked among the best French plays, each of its class.
Except these two pieces little or nothing of his has kept the stage or the shelves, but Sedaine may be regarded as the literary ancestor of Scribe and Dumas. He had the practical knowledge of the theatre, which enabled him to carry out the ideas of Diderot and give him claims to be regarded as the real founder of the domestic drama in France.
Sedaine, who became a member of the Academy (1786), and secretary for architecture of the fine arts division, died at Paris on the 17th of May 1797. He wrote two historical dramas, Raymond V, comte de Toulouse ou l'épreuve inutile, and Maillard, ou Paris sauvé.
His Œuvres (1826) contain a notice of his life by Ducis.