Delage was born and died in Paris. He first worked as a clerk for a maritime agency in Paris, and later as a fishmonger in Boulogne. He also served for a time in the French army, before embarking on a music career in his twenties. A student of Ravel, who proclaimed him one of the supreme French composers of his day, and member of Les Apaches, he was influenced by travels to India and Japan in 1912, when he accompanied his father on a business trip. Ravel's "La vallée des cloches" from Miroirs was dedicated to Delage.