Landslide susceptibility mapping is crucial for risk management in mountainous Nilgiris district, Tamil Nadu, India. In this study, the spatially distributed Stability INdex MAPping (SINMAP) model was used to develop a landslide susceptibility model for Coonoor watershed, which is based on a steady-state hydrologic model coupled with an infinite-slope stability equation. Shuttle Radar Topography Mission (SRTM) digital elevation model was utilized to compute the slope and other topographic parameters. In-situ data collection and laboratory tests were executed to estimate the hydro-geotechnical parameters. A detailed field study was conducted, and 35 samples were taken from the landslide locations to perform laboratory tests to find the geotechnical parameters. Also, an inventory landslide map was generated to evaluate the model performance. Statistical results of SINMAP show that, under the fully saturated condition, 58.96% of the region was found to be stable, 16.79% moderately stable, 8.72% quasi-stable and 15.24% unstable. The Area under the Curve (AUC) value of the predicted result is 72.3% which infer that the underlying predictors perform good in classifying the outcome. Thus, the considered parameters in the model have played its part well in the classification of the region based on its stability.