Xainza County on the Qiangtang Plateau (QP) spans a transitionally climatic and eco-environmental zone and is therefore a very sensitive region. Glaciers in this area are one of the most important kinds of land cover as well as key water resources, yet our understanding of their current status and spatio-temporal change remains limited. Using Landsat images, this study investigated the current distribution of glaciers (2015) in the Xainza Xiegang Mountains as well as the spatio-temporal changes that took place over six time periods between 1976 and 2015. Results show that, in 2015, 131 glaciers covered a total area of 74.59 ± 5.25 km², mainly located between 5,600 and 6,000 m above sea level (a.s.l). Between 1976 and 2015, the total number of glaciers increased by 12, while their areas decreased by 24.98% (24.83 km²). Glacial retreat has induced a loss of water resources of 11.77 × 108 m3 over the last 39 years, while spatial heterogeneities in glacial changes across various sub-basins, aspects, and altitudinal zones are also clearly observed. Climate warming is the key factor driving this continuous glacial retreat; the high-quality dataset presented in this paper for the Xainza Xiegang study area is crucial for the ongoing assessment of climatic and eco-environmental changes.