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A peculiar feature of the Himalaya is the occurrence of a system of low-angle-normal faults and shear zones, the South Tibetan Detachment System (STDS), at the mountain crests. The STDS was active during syn-convergent tectonics. We describe the STDS-related sheared rocks along the Dhauli Ganga valley, in the Garhwal Himalaya (NW India), where the Malari granite, reported as an undeformed igneous body cross-cutting the STDS, occurs. A detailed multidisciplinary study, integrating field-based, microstructural, petrographic and geochronological analyses was carried out on rocks along this valley. We demonstrate how the non-coaxial ductile portion of the STDS affected the upper part of the Greater Himalaya Sequence migmatite, which experienced peak pressure (P) – temperature (T) conditions of 0.9-1.1 GPa and ≥ 750°C at ≥ 24 Ma. This migmatite has been reworked structurally upwards leading to the formation of high-T sillimanite-bearing mylonites. Further upward, medium-T shearing deformed the Malari granite and leucogranite dykes, forming medium-T mylonites. Ductile shearing was temporally constrained, based on new in situ monazite datings and previously published Ar-Ar geochronology, between ~20-15 Ma. We demonstrate that a preserved ductile to brittle spatial and temporal transition of the STDS deformation exists, with the brittle features overprinting ductile ones. Our data shed new light on the geological evolution of the STDS in the NW Himalaya with implications for the relationship and relative timing of partial melting, granite emplacement and deformation along low-angle-normal faults.