In a post-health crisis context that has affected children's mental health and well-being, a territorial analysis confirms these observations and highlights concerns about addictive behaviour among young people. Based on this fact, a dynamic partnership between various players has been created in order to build a joint action. The aim of the project is to raise awareness among professionals working in childcare and early childhood structures of the importance of developing psychosocial competencies, so as to influence their development and children's health. This study allows - through intervention analysis - to understand the issues, levers and obstacles to partnership collaboration and the co-construction work carried out by all the players involved. Despite the obstacles encountered, the results demonstrate the added value of this approach and highlight the determining factors in its success.