The main purpose of this study is to investigate the relationship between firm-specific factors and capital structure with emphasis on the role of sanctions on listed companies in Tehran Stock Exchange. For this purpose, a sample of 154 companies listed in Tehran Stock Exchange during 2011-2019 is investigated and multivariate regression model based on panel data is used to test the research hypotheses. The results showed that there is a significant negative relationship between profitability and leverage based on book value and market value and there is a significant negative relationship between sanctions variable and leverage based on market value. However, there is a significant positive relationship between growth opportunities and leverage based on book value, which is in line with pecking theory. Also, according to the trade-off theory, there is a significant positive relationship between the size of the company and leverage based on book value and market value. However, no significant relationship is found between fixed tangible assets and capital structure.