In this study, we investigated the effects of debriefing on 196 Japanese University students as part of an international collaboration between Austria and Japan. Based on the results of our previous studies [19–21], we showed that debriefing can bolster learning from the perspective of attitude changes and performance in games. However, there were weaknesses to previous studies in the sense that there were no facilitators to conduct the debriefings. In the experiments, all types of debriefing were carried out by students, i.e. self-guided. However, debriefing is usually conducted by a facilitator and carried out in a group. To address this weakness, we introduced facilitator-guided debriefing for the experimental conditions. Therefore, there were two experimental conditions: facilitator-guided debriefing and self-guided debriefing. After debriefing, groups of four participants played the Highway Planning game, which deals with co-operation and conflict. According to the results, the participants under facilitator-guided debriefing conditions showed more cooperative attitudes than did those under self-guided debriefing conditions, while participants in the self-guided debriefing group showed more competitive attitudes.