Child and dyadic psychotherapy have been scarcely investigated from the psychotherapy process research perspective. Thus, content and mechanisms related to therapeutic change have been overlooked by research. This study aimed at testing the applicability of the generic change indicators (GCI) model to identify moments of change in the parent during dyadic interventions, as well as to explore, describe and illustrate the therapeutic process through a brief mentalization-informed intervention with a depressive mother and her baby, using video-feedback as its main strategy, which has ample evidence about its effectiveness. We conducted a single case qualitative study using the GCI model. The mother’s ongoing change was determined by identifying episodes of change (EC) and moments of change (MC). Each MC was then labelled with one of the 19 GCIs. GCIs were observed from the intervention’s start. GCI’s hierarchical levels were increasing over the intervention, in association with the video-feedback situation. Our findings suggest that the GCI model is feasible to observe and understand dyadic interventions, contributing to the growing body of evidence supporting psychotherapists’ training and supervision.