The purpose of this study is to verify the mediating effects of self-reflection in the influence of supervision experiences on countertransference management ability of play therapists. For this purpose, The Supervision Experience Questionnaire, Counselor Self-Reflection Scale, and Countertransference Factors Inventory(CFI) were used. The subjects of this study are 138 play therapists who have received the individual supervision at least three times. The results of this study can be summarized as follows. First, play therapists’ supervision experiences, the total score of Self-reflection and its sub-factors (self-understanding of counselor, 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-client interaction) had significant mediating effects on the relationships between play therapists’ supervision experiences and countertransference management ability. In conclusion, this study confirmed the mediating effects of self-reflection in the influence of supervision experiences on countertransference management ability of play therapists. Through this, the importance of the self reflection training in the play therapists’ supervision scene can be suggested.