When institutional frictions threaten to disrupt collaborations, an external authority can be brought in to resolve disputes. How effective is such external imposition? What are the institutional circumstances in which it works? Framed by the collaborative governance regime (CGR), which sees established procedures and institutions as a critical collaborative capacity, this research employs a unique concept—collaborative friction—to explore the role of external imposition in collaboration among entities with significant institutional differences. We examined 965 recorded collaborative frictions from four large collaborative infrastructure projects between governments in Hong Kong and mainland China. Our finding suggests a significant, but limited, effect of the central government’s imposition on collaborative frictions. We also find a significant role of sociopolitical circumstances in collaboration. Based on the findings, we make several theoretical propositions articulating external imposition’s role in collaboration.