of the core professional competences for running socio-educational groups with foster families. After a process of participatory action-research with 39 professionals from the Child Protection System from different regions of Spain, we see an improvement in the development of the competences necessary to establish a supportive relationship with families, management and group dynamics, as well as the crystallization of attitudinal changes in professional practices. Data have been collected on the basis of methodological complementarity and a pre-test–post-test design that has identified and explained the changes in the evolution of competences and professional practices.