Upper Fafan catchment of Ethiopia serves as the water supply sources. Groundwater is the major source water supply system in the region which needs critical attention for management particularly in the areas with high anthropogenic activities and intensive agricultural practices. Groundwater vulnerability assessment is a crucial step for the effective management of groundwater resources. This study aimed at assessing the groundwater vulnerability and spatial mapping by integrating the hydro-geological elements that influence and regulate groundwater pollution in the upper Fafan watershed using the modified DRASTIC model. A survey was conducted by collecting water samples from groundwater boreholes for nitrate and phosphate analysis which later were used for model validation. The Digital Elevation Model (DEM), land cover, and soil data were used for contaminant risk mapping. A total of seven parameters were used to evaluate the vulnerability of groundwater: depth to groundwater, net recharge, impact of vadose zone media, soil media, topography, aquifer media, and the permeability of the aquifer data. Using the modified DRASTIC model, an intrinsic and particular susceptible map was created. On the other hand, the spatial distribution of phosphate and nitrate contaminants was determined, where the result varies between 75 and 144 (low to very high, vulnerable zones). Accordingly, about 19.09% of the total area belongs to very low vulnerability, 14.43% to low vulnerability, 17.96% to moderate vulnerability, 37.95% to high vulnerability, and 10.58% to very high vulnerability classes. A good correlation exists between nitrate level and the intrinsic DRASTIC model, and between phosphate and the intrinsic DRASTIC model. The integrated vulnerability map showed high risk in the central and upstream parts of the catchment area. Therefore, improving the catchment's efficiency in using its current water supplies requires careful management of the groundwater source and quality protection. The output from this study would assist decision makers for proper planning and management of groundwater resources in the region. Key words: Groundwater, Modified DRASTIC, Upper Fafan Catchment, Vulnerability, and Water Quality.