Documents show that Campin was established as a master painter in Tournai in 1406. Two pupils are mentioned as entering his studio in 1427—Rogelet de la Pasture (generally identified with the great Rogier van der Weyden (Weyden, Rogier van der)) and Jacques Daret (Daret, Jacques). The only documented work by Jacques Daret, an altarpiece executed for the Abbey of St. Vaast near Arras, shows close stylistic analogies with works by Rogier van der Weyden on one hand and works earlier in style by the Master of Flémalle on the other. Both seem to proceed from common models, for they obviously are not copies of one another. As the Tournai records give the name of Campin as master of both Daret and Rogier, it has been generally assumed that the Master of Flémalle may be reasonably identified with Campin. Some scholars, however, have stylistically considered the works ascribed to the Master of Flémalle as early works by Rogier himself.

Campin's art is indebted to that of manuscript illumination, but his work displays greater powers of observation and ability to render plastic forms than is found in contemporary manuscript illumination. One of his masterpieces is the “Mérode Altarpiece” (c. 1428), a triptych of the Annunciation with the donors and St. Joseph on the wings (The Cloisters, New York City). The Virgin is portrayed in a setting of bourgeois realism in which interior furnishings are rendered with the frank and loving attention to detail that was to become a characteristic tradition of Flemish art. Another important work, at the Städelsches Kunstinstitut in Frankfurt am Main, consists of two wings of an altarpiece dating c. 1440 that are said to have come from the Abbey of Flémalle. They depict the Virgin and Child and St. Veronica (with Trinity on the reverse). Among other works generally ascribed to Campin are the “Virgin and Child Before a Firescreen” and a double portrait at the National Gallery, London, a “Nativity” at Dijon (dated c. 1430), and the “Werl Altarpiece” (1438) in the Prado, Madrid.