This study highlights the importance of social capital within third sector organizations, as in other sectors of the economy, and confirms the influence of social capital on human capital. In this case, it contributes to the analysis of the structure and quality of relationships among members of a social organization, which enables motivation and commitment to collective action. Based on exploratory and confirmatory factor analysis, from a 45-item survey applied to 190 workers in social organizations; the constructs were reconfigured for the construction of the model of organizational social capital, was carried out using the structural equation methodology. It is argued that the cognitive and structural dimensions of social capital affect its relational dimension in terms of identification, trust and cooperation, which in turn influences worker motivation and other key aspects of human capital. The relational dimension, measured by workers’ identification, trust, and cooperation, has significant effects on their motivation and work engagement, which leads to important practical considerations for human resource policies in these organizations. The article contributes to the existing literature on human capital management by exploring the perception of workers in nonprofit organizations that are part of Ecuador’s third sector.