Human impact plays an increasing role on vegetation change even on the Tibetan Plateau, an area that is commonly regarded as an ideal place to study climate change. We evaluate the nature and extent of human impact on vegetation dynamics by the comparison of two areas: the relative highly populated Lhasa area and a nearby less populated Lhari County. Our results indicate that human impact has mainly decreased vegetation greenness within 20 km of the urban area and major constructions during 1999–2013. However, the impact of human activities in a relatively large area is still minor and does not reverse the major trends of vegetation dynamics caused by the warming temperature in recent decades. It seems that the impact of anthropogenic factors on the normalized difference vegetation index (NDVI) trend is more apparent in the Lhasa area than in Lhari County. The major anthropogenic driving factor for vegetation browning in the Lhasa area is livestock number, while the factors, including the number of rural laborers and artificial forest areas, are positively correlated with the annual NDVI increase. The similar relationship between the annual NDVI and driving factors appeared in Lhari County, except for artificial forest areas. The warming temperature and the change in precipitation played dominant roles on vegetation greening in Lhari County than that in the Lhasa area.