Urban migration and population growth are increasing in a high degree. However, the level of urbanization does not correlate with the rate of urban growth therefore, leading to increase in numbers of urban poor. With the current global initiative of attaining sustainable development across human society, community engagement remains a key initiative towards achieving this development. However, creating and maintaining a sense of community is challenging in areas with high in-migration hindering the level of engagement. Therefore, the aim of this study is to understand the ability of people in community groups to participate in sustainable development. The theory of social capital developed through the actions of community group members is examined, and how the developed social capital contributes to sustainable development. The study was conducted in the poor neighborhoods of Nairobi city, Kariobangi. Interviews and Focus group discussion methods were used to collect information about the group activities which are assessed in terms of social capital they develop. The findings of the study were through community group variables of social capital identified as: improved sense of community, trust level, access to information, social support, and community involvement. These variables enhance community participation to development issues which has increased not out of advocacy, but due to trust and reciprocity. However, the implications of framing sustainable development through level of social capital at community level is discussed and possible insights for a more effective sustainable development is suggested.