This study presents a comprehensive assessment of slope stability along the Rudraprayag-Tilwara section of NH-107 in the Indian Himalayas, addressing the challenges posed by the geological setup and past deformation activities. The investigation employs both deterministic and probabilistic methods, utilizing the limit equilibrium technique and Monte Carlo simulation to evaluate the stability of weathered hill slopes. The results from deterministic analyses, employing Bishop’s, Janbu's, Spencer, and Morgenstern Price methods, reveal the factor of safety values close to unity, indicative of the presence of weak materials within the slope mass. However, these deterministic approaches, while providing conservative estimates, overlook the inherent uncertainties and variability in geotechnical parameters. The probabilistic analysis, specifically using Bishop’s method, sheds light on the vulnerability of the slopes, particularly site SL-3, with a reliability index of −0.313. The reliability indices for the other three sites also fall below the recommended limit for stable slopes (i.e., 3), suggesting potential susceptibility to failure. The comparison between deterministic and probabilistic results emphasizes the latter's realism in capturing the uncertainties associated with slope stability. The study underscores the significance of considering uncertainties in geotechnical parameters for informed decision-making in the design, construction, and maintenance of infrastructure projects in hilly terrains. These findings provide valuable insights into the complex dynamics of weathered hill slopes in the Himalayan region, contributing to the advancement of slope stability analysis methodologies and emphasizing their practical applicability in real-world scenarios.