This paper presented two non-governmental organizations' (NGOs') social capital development initiatives for social welfare in Bangladesh. This study was based on a qualitative case study approach using a multi-method data collection procedure, where a semi-structured interview, social mapping, participant observation, in-depth case study, focus group discussion (FGD), and documentation survey were employed. The study selected two NGOs such as Proshika and Practical Action Bangladesh (PAB) working with two indigenous communities, e.g. blacksmiths and goldsmiths. This paper considered the application of the main elements of social capital such as collective actions, social trust, coordination and cooperation of mutual benefits, and sharing norms and values. The findings showed that in many cases, NGOs' social capital development initiatives for social welfare were successful. The findings would be useful for the social workers, policy makers, development practitioners, and NGO managers.