Contrary to the widespread glacier mass loss in High Mountain Asia under global warming, glaciers in the Pamir-Karakoram region have exhibited anomalous less mass changes and even slight mass gains in recent decades. While geodetic studies have quantified decadal-scale mass loss, the process of glacier mass balance and its response to regional climate change remain poorly understood due to the scarcity of high-resolution observations. This study analyzes the characteristics of daily glacier mass balance and their responses to the heatwaves based on time-lapse photography, ablation stake/snow pit measurements and meteorological data collected at the Kangxiwa Glacier in the eastern Pamir. Our results showed that the Kangxiwa Glacier experienced weak mass loss in 2019/2000 and 2020/2021 balance years but significant mass deficits in 2021/2022 and 2022/2023. Observations evidence that the Kangxiwa Glacier is a spring-accumulation summer-ablation type, with spring (April–June) accumulation of +200–500 mm w.e. and summer (July–September) mass loss of 300–900 mm w.e. The unprecedented heatwave in July–August 2022 caused an abnormal mass loss of over -852 mm w.e. within 40 days, advancing the Glacier Mass Loss Day by one month and pushing the equilibrium line altitude above the glacier summits. The 2022 heatwaves, characterized by wakened westerly circulation, likely influenced not only the East Pamir region but also the western Kunlun Mountains, leading to increased incoming radiation and reduced precipitation. Our studies revealed that the high-elevation glaciers in eastern Pamir are sensitive to the heatwaves, suggesting that the termination of the so-called Karakoram anomaly may reflect recent climatic warming in this high-elevation region.