<jats:title>Abstract</jats:title> <jats:p>In eastern Africa, there are few long, high-quality records of environmental change at high altitudes, inhibiting a broader understanding of regional climate change. We investigated a Holocene lacustrine sediment archive from Lake Garba Guracha, Bale Mountains, Ethiopia, (3,950 m asl), and reconstructed high-altitude lake evaporation history using δ<jats:sup>18</jats:sup>O records derived from the analysis of compound-specific sugar biomarkers and diatoms. The δ<jats:sup>18</jats:sup>O<jats:sub>diatom</jats:sub> and δ<jats:sup>18</jats:sup>O<jats:sub>fuc</jats:sub> records are clearly correlated and reveal similar ranges (7.9‰ and 7.1‰, respectively). The lowest δ<jats:sup>18</jats:sup>O values occurred between 10–7 cal ka BP and were followed by a continuous shift towards more positive δ<jats:sup>18</jats:sup>O values. Due to the aquatic origin of the sugar biomarker and similar trends of δ<jats:sup>18</jats:sup>O<jats:sub>diatom</jats:sub>, we suggest that our lacustrine δ<jats:sup>18</jats:sup>O<jats:sub>fuc</jats:sub> record reflects δ<jats:sup>18</jats:sup>O<jats:sub>lake water</jats:sub>. Therefore, without completely excluding the influence of the ‘amount-effect’ and the ‘source-effect’, we interpret our record to reflect primarily the precipitation-to-evaporation ratio (P/E). We conclude that precipitation increased at the beginning of the Holocene, leading to an overflowing lake between ca. 10 and ca. 8 cal ka BP, indicated by low δ<jats:sup>18</jats:sup>O<jats:sub>lake water</jats:sub> values, which are interpreted as reduced evaporative enrichment. This is followed by a continuous trend towards drier conditions, indicating at least a seasonally closed lake system.</jats:p>