Plenty of progress has been made in the field of regional-scale slope stability mapping in response to the urgent need for effective ways to lessen the effects of both gravity- and earthquake-caused landslides. Darjeeling-Sikkim Himalaya has faced considerable slope instability issues attributed to a combination of factors such as rainfall, seismic shaking, complex lithological compositions and tectonic setting. In order to map the terrain stability in the region, Newmark displacement (Dn) model has been applied to estimate the Factor of Safety (FoS), Critical Acceleration (ac) and Displacement (Dn). Utilizing a geospatial dataset comprising a high-resolution digital elevation model (DEM), shear strength data for soil and rock obtained from an in-depth in-situ measurement using rotary drilling for estimating physical and shear parameters such as, unit weight, cohesion and angle of friction, etc., and surface-consistent peak ground acceleration (pga-g) with a return period of 475 years, these datasets have been converted into a grid with a spatial resolution of 12.5 × 12.5 m on Geographical Information System (GIS). The estimated of Factor of Safety (FoS), Critical Acceleration and co-seismic landslide displacement are calculated by integrating them into a dynamic model based on Newmark's Displacement. The calculated FoS ranges from 0.59 to 5.6, indicating that about 37% of the terrain becomes unstable as a result of rainfall and gravity-induced failure. The measured displacement (Dn) varies from 0 to 10 cm, suggesting that sliding blocks become unstable due to seismic shaking as well. This investigation provides future disaster mitigation and management strategies to address perennial landslide devastation caused in this terrain.