As international competition becomes increasingly globalized, the perspective on relationships among international firms is shifting from competition to cooperation. This reflects the growing importance of international interfirm cooperation, which was previously not regarded as a significant research subject in international business studies, and implies that efficient management of cooperative relationships is a prerequisite for success in international markets. From this perspective, this study proposes contingency-appropriate control mechanisms for curbing opportunism—the most critical factor impeding cooperation between joint venture partners in international joint ventures—and examines the effects of opportunism suppressed through such control mechanisms on relationship commitment and business performance as measures of joint venture outcomes. The results indicate that when asset specificity is high, ownership control as a transactional governance structure is most effective in curbing opportunism. However, when the environment is dynamic, the efficiency of transactional governance structures diminishes substantially, and instead, formalization as an administrative governance structure proves effective in suppressing opportunism. Furthermore, the findings reveal that opportunism curbed through appropriate control mechanisms has a favorable impact on joint venture performance.