This study aimed to measure the effect of social intelligence on organizational citizenship behavior and entrepreneurial behaviors among staff members in a sport organization in Iran, with the effect on social capital as a mediating variable. The method of this study was survey, and 205 staff members were selected using stratified random sampling. The instrument in this study included four standard questionnaires measuring social intelligence (Silvera, Martinussen & Dahl, 2001), social capital (Nahapiet & Ghoshal, 1998), OCB (Organ, 1988), and EB (Mirsafian & Salimi, 2016). The data was analyzed by employing SPSS and AMOS Graphics software. The results indicated that the staff’s social intelligence had a direct effect on improving the social capital of the organization (β = 0.63). Also, social capital had a direct effect on increasing the staff’s OCB (β = 0.20) and EB (β = 0.25). Furthermore, the staff’s social intelligence had an indirect effect on increasing the social capital and improved their OCB (β = 0.51) and EB (β = 0.44). Hence, trying to increase the staff’s social intelligence in sport organizations in Iran led to improving the staff’s extra role behaviors as well as entrepreneurial behaviors at the organization, in addition to the effect of increasing the social capital in those organizations.