Background and Objectives: Patient memory for psychological treatment contents is a promising transdiagnostic mechanism of change, but there is little consensus concerning its measurement. We investigated the relations between memory support, patient memory for treatment, and treatment outcome using a novel measure called the Conceptualization Task.Methods: Patients from a randomized controlled trial comparing cognitive therapy-as- usual to cognitive therapy plus the Memory Support Intervention (MSI) for adults with depression (N = 171) completed the Conceptualization Task and existing measures of memory for treatment. For the Conceptualization Task, patients read clinical vignettes and provided written responses to assess three facets of conceptualization ability: identifying contributing factors to psychopathology, making intervention recommendations, and providing a rationale for intervention recommendations. Higher scores were given to responses reflecting accurate memory for the theoretical model and change strategies used in treatment. Results: The Conceptualization Task was associated with select existing measures of memory for treatment. Therapist use of strategies from the MSI that involve patients constructing new ideas and connections about treatment contents (termed “constructive memory support”) predicted better Conceptualization Task performance. Patients providing more treatment- consistent intervention recommendations on the Conceptualization Task reported better treatment outcome. Yet the Conceptualization Task did not predict independent variance in outcome above existing measures of memory for treatment, suggesting that the task is too similar to previous measures. Conclusions: Memory support interventions may be improved by placing more emphasis on constructive memory support and reinforcing practical treatment contents (e.g., change strategies) over conceptual treatment contents (e.g., the theoretical model).