In 1930, Langlais won the premier prix in organ in Marcel Dupré's class at the National Conservatory. In 1934, he won a composition prize in Paul Dukas' class and, like Messiaen, was one of the composer's last students. Langlais studied improvisation with Charles Tournemire and received the Grand Prix d'Exécution et Improvisation des Amis de l'Orgue in 1931. He became organist for St. Pierre de Montrouge. During this time, Langlais composed his first works, the organ pieces Trois poèmes évangéliques (1932) and the 24 Pièces (1933-1939). In 1945, he joined the staff of the Institution des Jeunes Aveugles, where he was to remain for 40 years teaching and conducting the choir. Following in the steps of Franck and Tournemire, he became a professor at the prestigious organ tribune of Sainte-Clotilde in Paris, a position he held for the next 42 years. His immediate postwar compositions include the organ suites, his first Organ Concerto with orchestra (1949), and the famous choral Messe solennelle (1951), one of 13 masses composed by Langlais. The other most performed masses are the Missa in Simplicitate for chorus and organ (1953) and the impressive Missa Salve Regina for three solo vocalists, unison chorus, two organs, and eight brass (1954). The vast majority of Langlais' 254 compositions are on religious themes, although there are several concertos, organ symphonies, and individual secular pieces. Many pieces incorporate Gregorian themes that are varied with great originality and surrounded with expressive and splendid modal harmonies.
In 1952, Langlais visited the United States for the first time and proceeded to give approximately 300 recitals and hold many master classes there in the succeeding years. He composed numerous pieces for Americans, including an American Suite for organ (1959) and his Solemn Mass "Orbis factor" for chorus and organ, which was premiered in Washington, D.C., in 1969.
Between 1961 and 1976, Langlais taught French and foreign students at the Schola Cantorum in Paris. His later compositions include choral and organ works and chamber pieces for trumpet.