Financial flexibility means the ability of a company to access and restructure financial resources with minimal cost. Flexible companies are well able to survive financial pressures in times of negative shocks and financial crises, and easily obtain the funds they need for investment when profitable opportunities arise. Ultimately, the aim of this study is to examine the relationship between agency costs and financial flexibility with the moderating role of board gender diversity. The statistical population of the study is companies listed on the Tehran Stock Exchange and the sample under study includes 160 companies listed during the years 2019 to 2023. The research method is descriptive and correlational in terms of the relationship between variables and is applied in terms of purpose. The regression method and panel data as well as the fixed effects model were used to process and test the hypothesis. The results of the hypothesis analysis showed that board gender diversity has a negative and significant effect on the relationship between agency costs and financial flexibility.