In the wake of efforts to recover from prolonged political instabilities within MRU Countries,poor governance architectures, fragile institutions, and extreme poverty among citizens, local capital mobilization to fund investment initiatives seems impractical to harness the level of economic growth the region desires. Using its natural resources as a comparative advantage,the MRU region has attracted FDI to its extractive industries to support their respective countries' economic growth and job creation for their citizens. FDI plays a crucial role in the economic development of the region thus leading to our curiosity to explore factors determining its inflow into the MRU region. This study examines factors that determine FDI in the MRU and East African regions, focusing on the impact of the following variables; natural resources,GDP, inflation, infrastructure, merchandise trade, and domestic credit to the private sector. With the use of Hausman test approach for panel data model analysis, this study investigates the key determinant factors of foreign direct investment (FDI) in the Mano River Union covering the period from 2005 to 2021. Our research included four countries (Kenya, Rwanda,Tanzania, and Uganda) from the East African region as a comparative analysis for the study against the assumptions that FDI variables used for the analysis have contributed to economic growth in the four select countries of the East African Region. The data for this study were compiled from reputable sources such as the World Bank. The primary empirical estimating methodology is the random effect regression model, specifically suited to panel data. Complementary to the analysis to control for regional-specific effects, the least square dummyvariable model is used.