Research SummaryDrawing on signaling theory and the international business literature that addresses the role of institutions, we argue that multinational enterprises (MNEs) that use multimarket contact (MMC)—that is, meet the same competitors in multiple countries—to reduce rivalry in a given country, will have their actions and performance influenced by the institutional quality of that country. More specifically, we contend that action observability is the mechanism that explains why institutional quality facilitates an MNE's use of MMC with competitors in a host country. We also contend that an MNE's ability to successfully reduce rivalry with host country competitors via MMC is contingent on the institutional quality distance between the MNE's home and host country. We test our hypotheses with data from the mobile phone industry.Managerial SummaryMNEs often meet the same rivals simultaneously in multiple countries, a phenomenon known as market overlap or MMC. Prior studies have found that MMC deters rivals from attacking each other in the countries they have in common. However, these studies have not taken into account the heterogeneity of the institutional environments of the countries in which multimarket rivals compete. We contend that the quality of countries' institutions and the institutional quality distance between home and host countries affect the extent to which MNEs can observe each other's actions, which in turn helps rival MNEs to avoid mutually damaging moves for their sales performance in the countries they have in common.