Sociology as a science and a discipline emerge within the Catholic Church with the progressive recognition of the "social question" (synonymous here of the "labour question"). After the development of a tourvillian branch of the leplaysian sociology (Léon Gérin), a "doctrinal sociology" took roots with the denunciation, in the wake of social Catholicism, of the "undeserved misery" of the working class. By analysing the cases of the ACJC and the ACS, this article brings to light the rising interest for the social sciences in general, and sociology in particular, by the catholic youth movements, and define the scientific and disciplinary evolution that the passage from one movement to the other helped to establish.