Fossils are critical for understanding the uplift history of the Tibetan Plateau and its impact on the diversity and diversification of living organisms in Eurasia. However, well-preserved fossils, especially plant megafossils are rare in the plateau. In this paper, we describe two species of Koelreuteria, namely K. lunpolaensis sp. nov. and K. miointegrifoliola, based on exquisitely preserved capsular valves from the late Oligocene of the Lunpola Basin, central Tibet. Koelreuteria lunpolaensis is distinguishable from all extant and fossil species of the genus in the strongly asymmetric form of the capsular valves, the emarginate or lobed apex of the valves, and zigzag lateral veins that are tapering towards the margin of the valves, and is considered to represent an extinct lineage of the genus. Koelreuteria miointegrifoliola is most similar to K. bipinnata-type group of extant Koelreuteria. The diverse Koelreuteria confirms a warm and humid environment with a low elevation in central Tibet during the late Oligocene based on their modem distributions. Fossil evidence indicates that the Tibetan Plateau was a center for diversity and diversification of Koelreuteria in the Oligocene/Miocene. It also suggests that Tibet might also serve as a refugium for the K. bipinnata-type group in the late Oligocene.