This paper examines the influence of ethno-religious identity on the attitudes and behavior of faith-based nonprofit organization (FBO) staff when providing health and social services in international development. The paper focuses on contexts of ethno-religious violence, with specific attention given to the implications for potential service recipients’ inclusion and exclusion from services. Based on empirical evidence gathered during qualitative interviews with more than 100 NGO staff in Bosnia and Herzegovina, Lebanon, and Sri Lanka, the paper uses literature on the politics of collective violence to examine the ways in which FBOs generate bonding social capital and/or bridging social capital, and in some cases “block” the generation of positive social capital by mirroring, reinforcing, and reproducing societal divisions that are present in the cultures in which they operate. The data indicate that the polarization and boundary activation that result from collective violence cause FBOs that belong to the same religious groups involved in ethno-religious conflict to have high identity salience and high levels of bonding social capital. These organizations are more likely to serve the poor who belong to their own religious group. While much literature espouses hope for the potential of nonprofit organizations to generate bridging social capital, the data from this study indicate that in contexts of violence this is not the case for FBOs, who instead are likely not to serve community members of other ethno-religious groups. International FBOs whose religious groups have not been involved in the local conflict are susceptible to the same mechanisms because polarization and boundary activation cause low-income community members to categorize the international FBOs in local terms when determining whether or not to approach an organization for assistance. The results of this study have important implications for development policy, particularly in a policy environment where faith-based organizations are receiving increased attention and funding from public institutions providing development aid.