South Rimo Glacier, one of the largest glaciers in Karakoram, showed a glacier surge event during 2018–2020. To characterize the dynamics of the surge, we assessed surface height changes by differencing a time-series of DEMs produced from high-resolution TanDEM-X radar data. In addition, we evaluated the evolution of surface velocities with offset tracking using Sentinel-1 imagery. DEM differences show that the glacier started gaining height in the middle stream since 2013 where a bulge built-up and reached a maximum observed height of 28 m in 2017. After surge activation in 2017, the velocity increased by 2–3 order of magnitude with a peak velocity of 11 m/d in August 2019. Our work highlighted the value of high resolution DEM products and velocity maps in pre-identifying glacier surge and mitigating related hazards.