The purpose of this study is to compare the therapeutic alliance in two cases of couple therapy for treatment of depression, with the cases exhibiting different levels of Dyadic Adjustment and different outcome in terms of depressive symptomatology. Using the System for Observing Family Therapy Alliances, four dimensions of the therapeutic alliance (Engagement in the Therapeutic Process, Emotional Connection with the Therapist, Safety within the Therapeutic System, and Shared Sense of Purpose within the Couple) were analysed during the first, sixth and last sessions. The most notable differences were found in the Safety and Shared Sense of Purpose dimensions. The construction of safety within the therapeutic context appeared as an essential condition in the treatment process, especially for the case with a lower level of dyadic adjustment. However, having a Shared Sense of Purpose, the dimension which represents the within-couple alliance for the therapy, appeared as the essential condition to establish a context of mutual support in which the couple are seen working as a team to improve the symptoms of depression. The research questions and clinical implications arising from these contrasting cases study are discussed.