He became a novice in the Congregation of the Immaculate Heart of Mary, known as the Scheut Missionaries, in 1908, and was ordained a priest in July 1914.
He left for the Belgian Congo in December 1916 and was assigned to the Scheut fathers in Léopoldville, where he would stay over forty years.
In 1931 he built a first stadium, which was quickly deemed too small and was demolished in 1936 to make room for the consedrably larger Stade Reine Astrid.
Furthermore, he founded the newspaper La Croix du Congo, and some popular neighbourhoods (cités) for the inhabitants of Léopoldville.
Due to health concerns, de la Kethulle returned to Belgium towards the end of his life.
His remains were brought back to the Congo by boat and were buried in Léopoldville in the presence of more than 100 000 attendees.