The purpose of this study was to make a case study of applying sand play therapy to an adolescent with complex trauma experience caused by parental abuse and parental loss. It s specifically meant to investigate what changes there would be in the complex trauma experience of the selected subject during the process of sand play therapy, and to determine the effectiveness of sand play therapy. The subject in this study was a middle school boy in an urban community, who was at the western age of 13. From December, 2016, to December, 2017, sand play therapy that was based on Jung s analytical psychology was provided in 40 sessions, once a week, 50 minutes each. As for data analysis, the instruments of HTP, KFD, and KPRC were used to compare the state of the teenager before and after the sand play therapy was offered, and whether the therapy brought about any changes was analyzed from a perspective of ego development process. As a result, the client showed complex trauma symptoms at the initial stage of the counseling, and his ego state was confused due to the lack of safe protection. In the middle stage of the counseling, his inherent traumas that were related to negative maternity were healed through regression to the unconscious, and he gradually became immune to the impact of the unconscious. In the latter stage of the counseling, his ego-consciousness developed owing to the healing, and he experienced adaptive ego-integrity in daily routine life. Thus, there were positive changes in his overall main complaints. The findings of this case study illustrated that sand play therapy had positive effects on the psychosocial maladjustment of the adolescent with complex trauma experience.