Technical advancements have always been important in the construction of underground structures. The topographic, geological, and in-situ stress conditions directly influence the stability condition of an underground opening. Therefore, a proper and organized evaluation of the overall rock mass quality and analysis of the rock mass behavior must be carried out to predict the potential instability problems during the planning and design of an underground opening. The manuscript aims to characterize the rock mass quality condition and to analyze the potential instability issues that might be encountered during the excavation of the proposed Hemja-Patichaur road tunnel in the Western part of Nepal. The mapped geological and geotechnical parameters have been synthesized and presented. Assessed rock mass quality conditions along the tunnel alignment are illustrated using Q and RMR rock mass classification systems. More importantly, an evaluation of the stability condition and assessment of the required rock support measures using analytical and numerical approaches have been presented. All methods indicated the highest deformation at chainage 5+000m, where a weakness zone exists.