Gustaaf Flamen, son of Charles Flamen, merchant, and Anne Marcus, studied at the Brugean College of Saint Louis (1851-1857). Influenced by some of his teachers, e.g. L.L. De Bo and Verraes, he tended to flamingantism there and then already. Due to his music teacher Hyacinthe Labbe he discovered his musical talents, e.g. as a violin player. In 1857 he started his priestly training at the minor seminar in Roeselare. This training lasted four years, during which he had Guido Gezelle as a Dutch teacher. Subsequently he attended the major seminar in Bruges and was ordained priest there on July 9th,1862. He was appointed teacher at the college in Kortrijk (20.03.1862) and at the minor seminar in Roeselare (15.09.1867), where he and his colleague Hugo Verriest influenced Albrecht Rodenbach.
He was curator in Ruiselede (06.08.1873) and pastor in Meetkerke (07.04.1893), where Gezelle often paid him a visit. At his request, Gezelle wrote the poem "Te Meetkerke, in 't vet Moerenland" for the sexton-organist Hendrik Schramme.
He resigned from pastorship in Meetkerke on June 8th,1906 and on December 7, 1906 he became the principal of Saint Trudo's Abbey in Bruges. He wrote discourses in the Handelingen der gilde St.-Luitgaarde (Acts of the Saint Lutgarde Guild) in Bruges, and articles in Rond den Heerd (By the Fireside) and other magazines. He also published other works such as plays and historical dramas.