He studied the violin in Turin, Italy. From 1723, he played at the Concert Spirituel in Paris, the main semi-public music series.
In 1733, he was named "ordinaire de la musique" by Louis XV, but he resigned in 1737 after a clash with Guidon over control of the musique du Roy.
Leclair was then engaged by the Princess of Orange, and from 1738 until 1743 he served three months annually at her court in The Hague.
He returned to Paris in 1743, where his only opera "Scylla et Glaucus" was first performed in 1746. From 1740 until his death, he served the Duke of Gramont.
In 1764, he was found stabbed to death near his small house in a dangerous Parisian neighborhood.
Leclair was renowned as a violinist and as a composer: many suites, sonatas and concertos survive along with his opera, while some vocal works, ballets, and other stage music is lost.
His brothers Jean-Marie Leclair the Younger (1703–77), Pierre Leclair (1709–84) and Jean-Benoît (1714-after 1759) were also musicians.