Introduction: This study tries to find the association between “trust, social networks and Knowledge (as indicators of social capital)” and “Social Welfare” in Tehran. The questions of this study include: “What are the main Factors of social capital and social welfare in Tehran? Which of the eighteen indicators of social capital are effective on social welfare?

Method: Statistical population of this study includes people over 16 years in Tehran. 783 people from this city were selected randomly and data was collected by using questionnaire.

Findings: Among the 18 indicators of social capital in factor analysis, six factors “Social Communication, Solidarity and Social Integration, Informal charity, Religious and Reciprocal Participation, Attention to public affairs, Formal participation, Network of Friends, Colleagues and Kinships, Public, Individual and Institutional Trust, looking to the future and Security are effective in determine of social capital.

Discussion: The results show a significant relationship between social capital indicators and social welfare in Tehran. The major factors of social capital that increases social welfare (both Subjective and Objective) are: Security, Formal participation, Individual and Institutional Trust, Attention to public affairs, Network Kinships.