This study aimed to examine how students managed conflicts in an engineering design process and how different management styles affected their group interaction progress. We observed three groups of students in classes, where they designed devices to solve water shortages. Students' interactions involving conflict in these lessons were analyzed in terms of their conflict management style. Twenty conflict-based interactions were observed in the process of engineering design, and these occurred in all groups. Most conflict-based interactions we observed were task conflicts, and students showed conflict management styles of dominating, avoiding, obliging, integrating, and compromising. These different conflict management styles led to different amounts of progress in group interactions. Avoiding and dominating terminated interactions and prevented students from developing their ideas further. Dominating and obliging caused relationship conflict. Integrating and compromising management styles led to more productive student interactions. This study suggests that further educational efforts are necessary to teach students how to effectively manage conflicts in engineering design processes.