When counselors experience interpersonal stress, they appraise counseling events using a similar appraisal process as the well-known stress theory, the Transactional Model of Stress and Coping. Using structural equation modeling, we tested a mediation model representing the appraisal process in counselor interpersonal stress theory using a sample of professional counselors (n = 221). We hypothesized preventive resources and counseling self-efficacy would partially mediate the relationship between counselor interpersonal stress and counselor burnout. In the model, counselor interpersonal stress and preventive resources showed statistically significant direct effects on counselor burnout. Preventive resources partially mediated the relationship between counselor interpersonal stress and counselor burnout. Implications for clinical practice and counselor wellness are discussed.