The aim of this study is to investigate the relationship between social capital among employees with their job performance in Tehran's Forensic Medicine Organization. The study population consisted of all the employees of Tehran's Forensic Medicine Organization in 2015 that based on available statistics are 120 employees that because of limited statistical population, sampling has not been done. To collect data, two instruments were used to measure including social capital questionnaire of Nahapiet and Ghoshal (1998), with average reliability coefficient of 93% and job performance questionnaire of Hersey and Goldsmith Achiu model with average reliability coefficient of 88%. Descriptive statistics were used to describe the data and to analyze and evaluate the research hypotheses; test of inferential statistics including univariate regression analysis was used. While confirming the research hypotheses, results showed: Structural, cognitive and communicative dimensions of social capital of employees have an increasing and positive impact on their job performance and this effect is statistically significant.