This article details US officials’ mobilization of Puerto Rican labor during the occupation of the Dominican Republic (1916–1924) and the consequences for transnational working-class solidarity. It argues that the military government relied on Puerto Ricans as both imperial laborers and role models whose presumed cultural affinities with the Dominican populace would forestall resistance and contribute to efforts to reform Dominican society. Yet the rise of Dominican nationalist resistance forced Puerto Ricans to reconcile collaboration with their identity as Latinos and second-class American citizens. As they struggled to choose between conflicting loyalties, they were alternately labeled traitors to the United States or to their race. By the final years of the occupation, Puerto Ricans were condemned as colonial sepoys and abandoned by the very occupation they had helped to build. The article concludes that the Dominican case illustrates both US empire’s reliance on colonial labor and its limitations.