This study examines the impact of foreign direct investment (FDI) on financial development in D-8 countries. With the globalization process, FDI has become an important factor contributing to the deepening of financial markets and the development of financial intermediation. However, the extent to which FDI promotes financial development may vary depending on factors such as countries' financial structures, institutional quality and economic stability. In this study, the relationship between FDI and financial development is empirically tested using panel data analysis methods for the period 1991-2021. The findings reveal that FDI contributes positively to financial development, but this effect varies depending on the existing financial infrastructure of the countries. The results suggest that institutional capacity should be strengthened in D-8 countries to deepen financial markets and increase the positive effects of FDI on the financial system.