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Evapotranspiration (ET) is a key process of the climate system because it links water, energy and carbon cycles. In this study we modified a Penman–Monteith based algorithm to estimate ET on the Tibetan Plateau at a 1 km spatial resolution for the period 2000–2010 using meteorological and satellite remote sensing data. The results showed that the average annual ET on the Tibetan Plateau was 350.3 mm year⁻¹ and decreased from the southeast toward the northwest. The highest ET value was found in open water bodies (680.9 mm year⁻¹) and the lowest ET value was found in open shrubland (254.0 mm year⁻¹). Overall, the inter-annual ET decreased from 2000 to 2010 and there was significant negative ET trend over 42% of the region, primarily in the northwest of the Tibetan Plateau. Relative humidity was the dominant factor in controlling long-term variations of ET in the arid northwest plateau. But under moist conditions, leaf area index or temperature drove ET. In addition, P-ET on the Tibetan Plateau significantly increased and about 37% of the region showed strong positive P-ET trend primarily in the central of the Tibetan Plateau. The positive P-ET trend in four seasons suggested that the Tibetan Plateau might have become wetter during the past decade.