Deciding on capital structure is one of the most challenging and difficult issues faced by companies and the most critical decision regarding their continued survival. The most important factors in the capital structure of companies can be the quality of corporate governance as well as the behavioral factors of managers, because ultimately the management decides on the financing method. Therefore, the purpose of this study is to analyze the role of behavioral factors and corporate governance in the capital structure of companies. In order to estimate the research models, the annual data of 188 companies admitted to the Tehran Stock Exchange during the period of 2011-2021 and the Generalized Moments Method were used. Also, in order to extract and identify the behavioral variables, a qualitative approach and interview tools with experts have been used. The results related to the role of corporate governance in the capital structure of companies show that the indicators of corporate governance such as ؛ The dual duties of the CEO, the diversity of the board of directors, the independence of the board of directors, the gender of the CEO, the ownership of the board of directors, and the ownership of the CEO and the board of directors have a role in influencing the company's capital structure. On the other hand, the results related to the role of behavioral factors in the capital structure of companies show that behavioral indicators such as ؛ Overconfidence, management ability, managers' personality type, optimism, management tenure, narcissism, conservatism and short-sightedness have a role in influencing the company's capital structure. The efficient market hypothesis, which underlies conventional economic theory, is based on logical assumptions about efficient markets and profit maximization. However, the efficient market hypothesis is often unable to explain the chaotic phenomena observed in financial markets.