How vegetation phenology responds to climate change is a key to the understanding of the mechanisms drivinghis-toric and future changes in regional terrestrial ecosystem productivity. Based on the 250-m and 8-day moderateresol-ution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data for 2000–2014 in the Three-River Source Region (TRSR) of Qinghai Province, China, i.e., the hinterland of the Tibetan Plateau, weextrac-ted relevant vegetation phenological information (e.g., start, end, and length of growing season) and analyzed the changes in the TRSR vegetation in response to climate change. The results reveal that, under the increasingly warm and humid climate, the start of vegetation growing season (SOS) advanced 1.03 day yr?1while the end of vegetation growing season (EOS) exhibited no significant changes, which led to extended growing season length. It is found that the SOS was greatly affected by the preceding winter precipitation, with progressively enhanced precipitationfacilit-ating an earlier SOS. Moreover, as the variations of SOS and its trend depended strongly on topography, weestim-ated the elevation break-points for SOS. The lower the elevations were, the earlier the SOS started. In the areasbe-low 3095-m elevation, the SOS delay changed rapidly with increasing elevation; whereas above that, the SOS changes were relatively minor. The SOS trend had three elevation break-points at 2660, 3880, and 5240 m.