Triangular cooperation has attracted the attention of researchers as a rising trend of international development cooperation, yet questions have been raised about the location of political accountability within such complex networks. To explore these differences, this study compares two closely related cases, one bilateral (PRODECER, between Japan and Brazil) and the second a trilateral project that was modeled on PRODECER (PROSAVANA, between Japan, Brazil, and Mozambique). Through a longitudinal analysis of each case based on qualitative analysis of key policy documents and evaluations, the study explains the very different outcomes of these similarly designed projects as the result of triangularity’s effects beyond the state: an additional third actor and the disregard of the people led to the halt in the implementation of ProSAVANA. Triangular cooperation brought together a diverse range of domestic and transnational non-state actors together against ProSAVANA through the extension of networks, issue bundling, and information sharing. The formation of multiple networks provided civil society the means to share common issues. States then begin to be held accountable by their own citizens and international actors, but at the cost of project success. Through this analysis, the future possibilities for strengthening accountability mechanisms during triangular cooperation projects can be better understood.