High-altitude ecosystems, including the Tibetan Plateau, are crucial in global carbon cycling. However, their long-term carbon sequestration potential remains poorly understood. This study analyzes spatiotemporal NEP trends across the Tibetan Plateau (2001-2024) using an improved CASA model calibrated for high-altitude environments, integrating MODIS remote sensing and bias-corrected ERA5-Land climate data. 71% of the TP functions as a dominant carbon sink, with seasonal and spatial variations driven by climate and topography. NEP increased significantly (2.73 gCm(-)(2)yr(-)(1), p < 0.05), with summer productivity contributing 72.3% of annual carbon sequestration. Precipitation dominated NEP variability (significant positive correlations in 15.8% of vegetated areas), while temperature effects varied geographically, enhancing NEP in 32.3% of areas but reducing it in 24.1% of moisture-limited regions. The Hurst exponent analysis indicates that the eastern forested regions exhibit greater long-term carbon sequestration stability, whereas the western arid areas show higher interannual variability. With an average annual NEP of 86.5 gCm(-)(2)yr(-)(1), the TP plays a significant role in global carbon balance by acting as a substantial carbon sink in high-altitude ecosystems. These findings emphasize the need to integrate high-altitude carbon sinks into Earth system models and climate-mitigation frameworks. Future research should focus on improving high-resolution NEP monitoring through satellite-based validation, incorporating TP carbon dynamics into global climate models, and assessing the long-term stability under projected warming scenarios.