Decadal glacier thickness changes over the Upper indus Basin in the Jammu and Kashmir Himalaya were estimated using the TanDEM-X and SRTM-C Digital Elevation Models (DEMs) from 2000 to 2012. In the study area 12,243 glaciers having 19,727 ± 1,054 km 2 area have thinned on an average of − 0.35 ± 0.33 m a −1 during the observation period. The highest thinning of − 1.69 ± 0.60 m a −1 was observed in the Pir Panjal while as the marginal thinning of − 0.11 ± 0.32 m a −1 was observed for the glaciers in the Karakoram. The observed glacier thickness changes indicated a strong influence of the topographic parameters. Higher thickness reduction was observed on the glaciers situated at lower altitudes (− 1.40 ± 0.53 m a −1) and with shallower slopes (− 1.52 ± 0.40 m a −1). Significantly higher negative thickness changes were observed from the glaciers situated on the southern slopes (− 0.55 ± 0.37 m a −1). The thickness loss was higher on the debris-covered glaciers (− 0.50 ± 0.38 m a −1) than on the clean glaciers (− 0.32 ± 0.33 m a −1). The cumulative glacier mass loss of − 70.32 ± 66.69 Gt was observed during the observation period, which, if continued, would significantly affect the sustainability of water resources in the basin. The recent reports on the enhanced glacier-melt in the Himalayan region 1 encompassing the Upper Indus Basin (UIB) and the consequent impacts on the water, food and energy security 2 stimulated various scientific studies to investigate the health and dynamics of glaciers in the UIB 3-5,7-16. However, most of the studies have focussed on the changes in the glacier area, snout recession, Equilibrium Line Altitude (ELA), impacts of the increasing temperatures, the influence of debris-cover 4,5. Glacier mass balance is the most important indicator of glacier health and is regarded as the direct and immediate glacier response to any changes in climate 6. However, glaciological mass balance, though considered more accurate method for glacier mass balance, is restricted to a few glaciers in the UIB owing to its rugged terrain, logistic challenges and security impediments 3. In view of these constraints, the geodetic mass balance has emerged as a credible alternate approach to assess glacier mass balance changes at local and regional scales in the UIB 7-15. The past studies have reported significant variability in glacier mass changes over the High Mountain Asia (HMA) region. Gardelle et al. 15 for instance, provided comprehensive regional mass balance estimates over the Hindu-Kush Karakoram Himalaya (HKH) region between 2000 and 2011, and highlighted the higher mass wastage in the western Himalaya, moderate mass loss in the eastern and central Himalaya, small mass losses in the Hindu-Kush and stability or even slight mass gain in the Karakoram and Pamir sub-regions. The variability in the mass balance of glaciers in various Hindu-Kush Himalayan regions has been largely attributed to the peculiar topographic and climatic setting of each of the mountain ranges 16. However, it has been observed that the...