This study aimed to examine whether countertransference feelings mediate the relationship between a play therapist's countertransference management ability and vicarious trauma when counseling children who have experienced trauma. The participants included 113 play therapists in Seoul and Gyeonggi-do, all of whom held a master's degree or higher and had experience in child trauma counseling. Data analysis employed SPSS 26.0 and the PROCESS macro ver. 4.0, specifically Model No. 4. First, the key finding indicates a verified mediating effect of countertransference feelings in the relationship between a play therapist's countertransference management ability and vicarious trauma. Second, in the relationship between a play therapist's countertransference management ability and vicarious trauma, only the sub-factor ‘rejection’ among the sub-factors of countertransference emotions demonstrated a mediating effect. The study provides foundational information on vicarious trauma experienced by play therapists and establishes the importance of therapists' countertransference management skills and emotional attunement in influencing vicarious trauma.