The purpose of this research is to investigate the effect of CEO's financial expertise on financial performance and investment efficiency of companies. By increasing the CEO's financial expertise, it is expected that the CEO's ability to analyze and make financial decisions will improve, which can lead to increased financial performance and improved investment efficiency. The nature of the current research is quantitative and in the group of positivist researches; Because the investigated concepts exist objectively in the external world, and the researcher and the reality of the subject are completely independent from each other. Since the method of this research is based on describing the real connections between the available data (description of what is) which is presented in the form of a model, the research is considered in the field of descriptive research. In this research, in order to investigate and analyze the hypotheses, the data related to 181 companies admitted to the Tehran Stock Exchange for the period of 2016 to 2016 were extracted and combined data regression models with the generalized moments approach (GMM) and Stata version 17 software to test the hypotheses. And Bidel's (2009) model has been used to measure investment efficiency. Also, financial performance is measured through return on assets. The CEO's financial expertise significantly leads to increased asset returns and improved investment efficiency in companies. These results are consistent with the existing theoretical foundations in the financial field, which emphasizes the importance of managers' financial knowledge and expertise in improving financial performance and investment productivity. In general, it can be concluded that the CEO's financial expertise not only leads to more effective financial decisions, but can lead to overall improvement in financial performance and optimal use of capital resources.