Although institutional environments are important determinants of transaction costs in IJV management and performance, prior studies have paid limited attention to their impacts on partner opportunism. Building on institution theory, this study examines how the characteristics of the host country government affect IJV foreign partner opportunism. The authors posit that host government resource dependence and policy uncertainty increase foreign partner opportunism, and their impacts are constrained by formal (i.e., contract specificity) and informal (i.e., shared vision) governance mechanisms, respectively. The empirical results from a primary survey of IJVs show that contract specificity is effective in curtailing the effect of resource dependence on foreign partner opportunism. In contrast, shared vision weakens the effect of policy uncertainty on foreign partner opportunism. These findings provide important research and managerial implications on how to manage foreign partner opportunism in IJVs.