This study reviews the creation and testing of a model of Therapist Personal Agency during MFT training. A model including self-efficacy, trainee developmental level, supervisor working alliance, family of origin relationships, and psychological states was supported by data collected from a national sample of MFT students. The model supported by the data was consistent with much of the previous research regarding the correlates of therapist self-efficacy. Furthermore, the model accounted for 20% of the variance in therapist performance as measured by therapist reports of the working alliance. The results also highlighted the importance of attending to the relationships, interactions, and experiences that take place within the training environment and secondly, the added value that may accrue from focusing on the trainee's extended network of family relationships. A brief case example serves to illustrate the importance of tending to Therapist Personal Agency. In sum, this study provides preliminary support for holistic training methods that focus upon the whole person of the therapist.