Previous research has consistently found self-assessment bias (an overly positive assessment of personal performance) to be present in a wide variety of work situations. The present investigation extended this area of research with a multi-disciplinary sample of mental health professionals. Respondents were asked to: (a) compare their own overall clinical skills and performance to others in their profession, and (b) indicate the percentage of their clients who improved, remained the same, or deteriorated as a result of treatment with them. Results indicated that 25% of mental health professionals viewed their skill to be at the 90th percentile when compared to their peers, and none viewed themselves as below average. Further, when compared to the published literature, clinicians tended to overestimate their rates of client improvement and underestimate their rates of client deterioration. The implications of this self-assessment bias for improvement of psychotherapy outcomes are discussed.