Landslides occur frequently in the Himalayan region, especially during the monsoon season. Stability assessment of any landslide site provides a good understanding of the shear-strength response of the in-situ geomaterials and causative factors. Often the sliding geomaterial is a complex mixture of soil and rock pieces in the form of debris underlain by jointed rock strata (bedrock). Testing of these materials in the undisturbed state is generally not feasible, and hence, the shear-strength parameters are derived through simple field investigation, index testing and classification. In the present study, a methodical procedure involving field investigations and laboratory studies was adopted to carry out stability assessment of a landslide site in the Lesser Himalayan region. The field investigations included a ground-penetrating radar (GPR) study, mapping of joints in the rock mass and collection of debris and rock samples. Apart from it, laboratory studies included an X-ray diffraction (XRD) analysis of the sand-fines matrix, index testing of soil samples, direct shear tests on debris samples and point-load strength-index testing on rock chunks. Laboratory tests were performed using conventional triaxial and a state-of-the art large-sized direct shear experiments. For large-sized direct shear testing, the gravel fraction was varied to quantify the effect of gravel content on the internal friction angle (ϕ). The parameter, cohesion of the debris was derived through back-analysis method. The rock mass rating (RMR), tunnelling quality index (the Q-system) and the geological strength index (GSI) were used to characterise the rock mass whereas, the shear strength parameters of the rock mass were derived through two non-linear strength criteria. Initial estimates of the shear-strength parameters of debris and the rock mass were employed to obtain the factor of safety (FOS) of the slope, which was found to have been underestimated. Back-analysis was then used to adjust the shear-strength parameter for cohesion. These adjusted parameters were then used to assess the stability of the slope and to suggest remedial measures.