The South Slope of the Himalayas (SSH) is witnessing dynamic shifts in vegetation greenness driven by climatic conditions across elevation variability. Here, we analyzed greening patterns of natural vegetated surfaces along the elevational gradient and examined their connection to climate changes from 2000 to 2022. Over 50% area of SSH exhibited significant greening, with higher rates in Central Himalayas (CH) and Western Himalayas (WH) compared to Eastern Himalayas (EH). The relative change rate (RCR) showed a notable increasing vegetation greenness from similar to 2,600 to similar to 5,000 m, followed by a decreasing trend in all subregions. Results showed that air temperature promoted the vegetation greening significantly in the high mountains but caused heat stress in lowlands of CH and WH. Precipitation supported growth in the middle mountains across the region except EH, which faced waterlogging stress. These findings are valuable for understanding vegetation changes under future climate changes and advancing our knowledge of ecosystem responses.