ABSTRACT Despite its importance for therapeutic work, therapists’ experiences in perinatal psychotherapy remain largely underinvestigated. This qualitative study examined therapists’ experiences in addressing intergenerational adversities in perinatal women with adverse childhood experiences. It specifically emphasized the negotiation of the “motherhood constellation” and the relational changes in the mother – grandmother relationship nearing and after birth. Data from individual interviews and a follow-up focus group with seven therapists were analyzed via reflexive thematic analysis. Two main themes with associated subthemes were derived from the data: (1) therapists’ experiences with unexpected changes toward closeness in the mother – grandmother relationship during pregnancy and postpartum and (2) therapists’ attempts to understand why some women change from perceiving their mother as an adverse caregiver to their closest support in their transition to motherhood. The therapist’s empathic and reflective capacity was challenged by abrupt changes in mother – grandmother relationships. Their attempts to make sense of the changes ranged from expected developmental processes to more pathological processes. The findings from the present study highlight therapeutic challenges in working with mother – grandmother relationships in the perinatal period and the importance of therapists having multiple perspectives in their understanding of intergenerational relational changes.