This study examined the multifaceted nature of Social Capital (SC) in community development projects by using Water, Sanitation, and Hygiene (WASH) interventions in three urban Bangladeshi slums as a case study. Despite its recognized importance, the ambiguity surrounding SC has led to mixed outcomes, necessitating a more theorized approach to quantitatively assess SC. To address this, a comprehensive methodology was developed, specifically crafted for a community development context and incorporating standard SC questions, social network analysis indices, and an adherence to social norms through behavioral game theory. The analysis revealed varied SC profiles, with one slum achieving successful community toilet management through strong reciprocal ties. The other slums faced challenges due to community division and weakened SC among key individuals. These findings underscore the necessity of tailoring interventions to community‐specific SC characteristics. The streamlined approach derived from the study provides guidance for both enhancing the effectiveness of community interventions and advancing sustainable development.