Cash flow is a measure of corporate performance and shows the cash that the company has after making the necessary expenditures to maintain or develop assets. The amount of operating cash flows is one of the main indicators for evaluating the extent to which the operations of the business unit have generated sufficient cash flows to repay loans, maintain the operational capacity of the business unit, and pay dividends, and make new investments possible without relying on financial resources outside the business unit, and examining the factors affecting it is important for the company. Therefore, the purpose of this study is to study the effect of board size on the relationship between managerial shortsightedness and operating cash flow. The statistical population of the study is companies listed on the Tehran Stock Exchange and the sample under study includes 152 companies listed during the years 2018 to 2022. The research method is descriptive and causal-correlation in terms of the relationship between variables, and it is applied in terms of its purpose. To process and test the hypotheses, regression method and panel data as well as fixed effects model were used. The results obtained from data analysis show that board size has a negative and significant effect on the relationship between managerial myopia and operating cash flow.