Holocene sediments from a 9m high outcrop at the Gangyasang Qu's entry into Lake Nam Co, on the south-eastern Tibetan Plateau, were studied in a multiproxy approach. The lowermost part of the section is of early Holocene age and consists of varved sediments deposited in a proglacial lake. Geomorphological investigations of fossil beach ridges and fossil cliff lines in the littoral zone of Nam Co indicate a late Pleistocene lake level high of 29m above the present level. A warming is visible in ostracode-rich silts deposited after 9.6kaBP. An ostracode-based transfer function estimates a lake level 28m higher than today from this time until about 5.2kaBP. A late Pleistocene lake level high was accompanied by an increase in lake size, causing Nam Co to overflow into the lower course of Gangyasang Qu, where a bay with slack-water conditions formed. Between 4.2 and 1.3 ka BP the lake level was approximately 10 m higher than today. The progradation of the Gangyasang Qu delta into Nam Co and the decreasing lake level shifted the study site into a fluvio-lacustrine environment. The sandy character and relatively low numbers of ostracode valves in the topmost sediments indicate increased fluvial activity, possibly due to a temporary increase in flood frequency. This facies lasted at least until 1.3 kaBP, when the lake level of Nam Co dropped again and the river incised more than 10m into the underlying fluvio-lacustrine and lacustrine sediments.