Nepal, being a mountainous country, faces numerous road hazards such as landslides, subsidence, and rockfalls, among other geological hazards. A significant issue in roadway development is ensuring stability and safety in challenging terrain. This research focuses on conducting engineering geological mapping, rock mass classification, and recommending feasible support systems for the proposed road tunnel from Barghat to Dumkibas, situated within the Mahendra Highway and part of the Siwalik Group comprising sandstone, mudstone, and conglomerate formations. The Q-system and Rock Mass Rating (RMR) system were utilized for rock mass classification, revealing Q-values ranging from 0.495 to 1.33. This indicates a range from poor to very poor rock mass based on the Q-system. RMR values ranged from 28 to 39, also suggesting poor rock mass condition. Based on these findings, a potential support system for the proposed road tunnel was recommended. Furthermore, a kinematic analysis conducted for slope stability revealed potential failure modes such as plane failure, wedge failure, and toppling failure. This provides crucial insights for implementing suitable engineering solutions to ensure the safety and stability of the proposed road tunnel within the challenging geological conditions of the Mahendra Highway area.