NH 1 has always been a national highway of high strategic importance, whether from a defense or civilian point of view. The highway connects Srinagar with Leh in Ladakh. Ladakh remains cut off for 5–6 months from the rest of the world from November to April due to heavy snowfall at Zojila Pass. The rock stability analysis along NH-1 is important for the smooth operation of traffic flow. The primary goal of this study is to carry out a geotechnical stability analysis along the NH-1D in Ladakh. The study was carried out with the help of a review of recent literature and relevant field tests. The methodology consists of calculating the rocks’ Rock Mass Rating (RMS) values, followed by their kinematic analysis. The field studies consisted of the identification of instability-prone sites, the collection of discontinuity data, the assessment of groundwater conditions at 38 vulnerable locations from Kargil city 0 km to Leh town 211 km, and the carrying out of a point load test. A thorough geotechnical analysis improves our understanding of stability along the strategic highway. We had done rock slope stability analysis on 38 sites by using rock mass rating (RMR) followed by slope mass rating (SMR). Notably, 29% fall into the “fair” category, while 71% fall into the “good” category. However, there are a few sites like site 8 (19.3 km), site 13 (24.9 km), site 15 (27.5 km), site 18 (30.9 km), site 27 (115.2 km), and site 29 (117.2 km) that fall under the “marginally good” category. This classification indicates that many sites are prone to slope failure and require immediate measures against stability. We have selected site 9 (20.6 km), site 14 (25.6 km), site 16 (27.9 km), and site 28 (116.3 km), as these sites are very critical and prone to failure, to do numerical modeling under the static and dynamic load to evaluate the seismic vulnerability of these slopes. To improve our knowledge, this study takes a novel approach involving seismic vulnerability assessment. Numerical modeling of selected sites uses historical earthquake data to simulate and analyze the slopes’ response to earthquake loads. This comparative study aims to reveal the relationship between rock classification and seismic susceptibility, thereby providing valuable insights into slope behavior under earthquake loading conditions. The findings of this study not only contribute to the immediate need for stability measures along NH-1 and offer a novel perspective on how rock classification can be used as an early indicator of seismic susceptibility.