This research is a case study on a child with peer relationship difficulties. The purpose of this study is to analyze the theme of play in school play therapy and to examine its therapeutic effects. Participant in this study was elementary school boy in 3rd grade. The child client's play therapy was based on the Child-Centered Play Therapy, and 55 sessions were held, and parent counseling and teacher counseling were conducted. Child client showed the theme of Hopelessness, Revenge, Power/Control, Separation, Mastery, Protection, Nurturing, Resiliency, Safety, Relationship in play therapy. Through the play themes, child client expressed and solved his psychological difficulties.