This research reports the effectiveness of traditional games in reducing posttraumatic stress disorder or PTSD in elementary school students. The study employed a quantitative approach and experimental method with a one-group pretest-posttest design. The research sample was 5 and 6 graders of elementary school students, which involved 85 students in total. The intervention was carried out through several stages, namely Beginning a Group, The Transition of a Group, Working in a Group, and Terminating of a Group. The instrument used to measure the effectiveness of the intervention was the problem checklist of PTSD and in this study, the instrument was analyzed to determine its validity in measuring the effectiveness of the intervention. The data obtained were analyzed using the RASCH Model with the WINSTEP application. The results show that the instrument used to measure the intervention has excellent reliability and meets the unidimensionality requirements. However, items number 1 and 54 were declared invalid. In addition, traditional games are concluded to be effective in reducing stress disorders in students. This change occurred in the majority of students which even give a significant impact on some students. However, most of the students still had no change and even tended to have an increased post-traumatic stress disorder. Based on these findings, it is expected that traditional games can be beneficial primarily to reduce post-traumatic stress disorder.