This paper explores the relationship between epistemology and psychotherapy, examining the possible role of therapists' epistemic commitments on their psychotherapeutic outcomes. The epistemic match between therapists' worldviews and their psychotherapeutic practices are viewed as a potential source of the allegiance effects that are commonly cited in the psychotherapy literature. This notion is examined in relation to current literature concerning psychotherapy process and style, and examined in an exploratory study of psychotherapy outcomes. As expected, results indicated that when therapists conducted a constructivist form of therapy, Coherence Therapy, stronger commitments to constructivist beliefs were linked to more effective psychotherapy outcomes. The implications of these findings are discussed in relation to the overall role of epistemic commitments in guiding psychotherapeutic practices in a way that might inform an understanding of allegiance effects in counseling and psychotherapy. © 2010 Taylor & Francis.