The purpose of this study is to verify the mediating effects of self-reflection on the influence of self-efficacy on countertransference management ability of play therapists. The subjects of this study are 176 play therapists who have worked in the field of play therapy in Korea. The results of this study can be summarized as follows. First, play therapists’ self-efficacy, the total score of Self-reflection and its sub-factors (self-understanding of counselor, counselor expertise, counselor-client interaction), countertransference management ability had a positive correlation. Second, the total score of Self-reflection and its sub-factors (self-understanding of counselor, counselor expertise, counselor-client interaction) had largely mediating effects on the relationships between play therapists’ self-efficacy and countertransference management ability. In conclusion, this study confirmed the mediating effects of self-reflection on the influence of self-efficacy on countertransference management ability of play therapists.