<p>Over the past century, numerous studies have examined Jean Piaget’s relationship with psychoanalysis. Until the 1970s, they often emphasized the value of a rapprochement between Piaget and Freud and highlighted the use of Piaget’s ideas in therapeutic practice. Then from the 1980s onwards, several studies focused on the relationship between his work–seen as purely cognitive, to the exclusion of the social and the affective–and his conflicted relationship with his mother. Based on similar sources, particularly his autobiography, these studies led to a reductionist account of his work according to which intellectual content was determined as much by the conflictual relationship as by his alleged autism. The article begins by deconstructing these ideas, showing that in the 1920s Piaget gave an important place to affectivity and the role of the mother in development. It then analyses the Piaget’s family dynamics of the 1919–1920 period, focusing on the family system–Jean’s parents, sisters and brother-in-law–in its relationship to pathology, a dynamic reconstructed with the help of correspondences. The article presents a series of totally unknown episodes in Piaget’s life. It shows that this was an enmeshed family system Minuchin (Families and family therapy, 1974) in which members were both highly involved and dependent on the mother. Within it, Piaget was designated as a <i>therapist</i>, for both the mother and the system, thus reversing standard roles and the classic figure of the designated patient. This research strengthened the few works that have identified either Piaget’s position as a therapist or the importance of his ideas for psychotherapy.</p>