Lake-sediment cores from Heywood and Sombre Lakes on Signy Island (South Orkney Islands), Antarctica, have yielded a conformable radiocarbon chronology for the Holocene and a high-resolution record of environmental change. The lakes share a common climate and geology but have distinct catchments. This provides an opportunity for using lake sediments to differentiate between local, within lake/catchment, events and those at a regional scale. Analyses of various biological and physical remains from the lakes suggest that both catchments have undergone considerable changes during the last 5700 years. Macrofossils (moss and crustacean remains) are more abundant in the late Holocene, being associated with a period of high sediment accumulation, which is related to diatom evidence for more nutrient-rich conditions at the sites. This is interpreted as a response to a Holocene‘climate optimum’ at c. 3800–1300 14C yr BP. The record is consistent with other lake, ice and ocean core studies, although the climate optimum appears to have persisted for a longer period at Signy Island.