The breeding distribution of the Upland Buzzard (Buteo hemilasius) is restricted to the eastern Palearctic. In comparison to other Buteo species, little is known about this species' breeding ecology. The objectives of our study were to describe nest sites and reproductive success of Upland Buzzards in Mongolia. The average clutch size for 304 breeding attempts in 2001–07 was 3.49 eggs (±1.09 SD; range 2–8; total of 1061 eggs laid). For 215 breeding attempts, the average brood size was 1.95 nestlings (±1.53; range 0–6). We found that the nest materials and nest size varied greatly, probably corresponding to the availability of nesting materials within the territory. However, the variation in nest size may also reflect the fact that some of the smaller nests were built on human-made structures, such as electric pylons or roofs of small buildings.