Objective: The operationalization and the role of a participatory model of diagnostic and therapeutic formulations called Foster Groups, implemented in a Community Mental Health Center in Lima, Peru, are analyzed. Material and Methods: The research was based on the participanting observation by experts in community mental health, public health, communication and social sciences, of a total of 24 Foster Group sessions held at the Nancy Reyes Community Mental Health Center in Chorrillos, Lima Peru, during the years 2018-2019. Results: The Foster Groups are structured in sequential phases that follow a logical process of diagnostic formulations and management plans, concurrently performed by professionals from different disciplines for a small group of users, thus allowing both, diagnoses as plans, to be more comprehensive. An environment of trust is generated, allowing people to share expe...