He is considered alongside André Grétry and François-André Danican Philidor to have been the founder of a new musical genre, the opéra comique, laying a path for other French composers such as François-Adrien Boieldieu, Daniel-François-Esprit Auber, Charles Gounod, Georges Bizet, and Jules Massenet in this genre.
As the eldest child, in 1749, a few months after his father's death, he left for Paris with only a few coins in his pocket, a violin and a recommendation letter, in an attempt to further his musical career and provide for his siblings.
In 1752, after watching a performance of La serva padrona by Giovanni Battista Pergolesi at the Paris Opera, he decided upon his true vocation.
Secretly, with a text by La Ribardière, he wrote Les aveux indiscrets, his first comic opera, which premiered at the theater of the Foire St Germain in February 1759.
Michel-Jean Sedaine, a well-liked librettist, proposed to Monsigny a collaboration, following Le cadi dupé's success.
It is during this same year of 1768 that the composer purchased the post of maître d'hôtel in the service of the great courtier Louis Philippe I, Duke of Orléans.
Hearing of the composer's state of poverty, the members of the Opéra-Comique gave him a pension of 2400 pounds, in order to prove their gratitude to one of the founders of their theater.