The analytical framework of social capital emphasizes that socialization of individuals results from participation in associative groups, and this socialization serves to include certain shared norms and encourage cooperative and participative social action. Proponents of the social capital framework believe that community or associative life has functions in order to build trust, strengthen broad social networks, and establish norms that maintain and empower healthy social systems. In this regard, "religion" has been proposed as one of the important factors in the production and strengthening of social capital in societies, and arguments have been made by sociologists to rationalize this relationship. In the present research, first, the arguments aimed at the mechanisms of social capital production by religion were translated into hypotheses about how religion is related to social capital. Then, an attempt was made to empirically test the validity of these hypotheses with the inter-country comparative method in Iran by placing the "county" as the unit of analysis and using secondary data. The findings related to the empirical test of the hypotheses of this research showed that even when the effects of various development indicators are controlled and removed, religion is still an influential factor in strengthening social capital in Iran.