He is believed to have been a ballet dancer in Turin, Italy.

While he was in Turin he studied composition and violin under Somis.

He returned to France to settle in Paris and, in 1734, he entered royal service, but resigned four years later to devote himself to concert tours.

Leclair held several posts in various courts. His later patrons included Anne, Princess of Orange, in The Hague, and finally the Duke of Gramont, a former pupil.

He retired to a quarter of ill-repute in Paris where, in 1764, he was found murdered in his lodgings, perhaps by his nephew who was also a violinist.

Although he also wrote music for the theatre, including an opera, "Scylla et Glaucus" (1746), Leclair is chiefly known for his violin music and in particular for his first two published sets of violin sonatas.

The first set of twelve, published in 1723, includes two also for flute and basso continuo, and the second dozen includes five also for flute as a possible alternative to the violin.