The need to reexamine the sustainability of just war and nonviolence as means of resolving conflicts in this contemporary era has created an ethical dilemma between justice and peace. Some recent studies conducted in this regard tend towards nonviolence and advocate for a complete abandonment of the just war ethics because of its inability to protect innocent civilians. Consequently, this study aimed to investigate the polarity between the just war theory and nonviolence and their relevance to contemporary society. The research analyzed diverse literature and established that the just war theory is still relevant for just defense. However, to prevent using the just war theory to promote offensive wars, it has been affirmed that it should be renamed as ‘ethics of peacebuilding,’ which could support nonviolence and dialogue to achieve sustainable peace. Since the just war theory is well developed in Catholic theology, the study suggests further research on nonviolent communication which expands ethics of nonviolence and provides practical skills for dialogue.