In this study, we reconstruct high-resolution vegetation and climate variability over the past 6100 years using a multi-proxy approach (i.e., pollen, stable organic carbon isotopes (delta C-13), and environmental magnetic parameters) from an alpine peat sequence of the Dayara meadow, located at similar to 3430 m altitude in the upper Bhagirathi basin of the Central Higher Himalaya. The chronology of the studied lake-peat sequence, constrained by four radiocarbon (C-14) ages, indicates that peat development in the region commenced around 6100 cal yr BP. Pollen combined with delta C-13 results reveal a significantly warmer and wetter climate between similar to 6100 and 5300 cal yr BP, corresponding to the late phase of the Holocene Climate Optimum (HCO) in the upper Bhagirathi basin. Around similar to 5300 cal yr BP, an abrupt climate shift occurred, which led to a prolonged dry spell between similar to 4800 and 3400 cal yr BP. This dry spell was characterized by a decline in arboreal tree taxa, particularly Quercus, Alnus, and Betula, the complete disappearance of Juglans, and a notable increase in drought-tolerant herbs, such as Chenopodiaceae-Amaranthaceae and Ephedra. This prolonged cold-dry phase is correlated with a weakening of the Indian summer monsoon (ISM) intensity, as previously recorded in the core summer monsoon zone, in response to regional warming of the Indo-Pacific Warm Pool. Subsequent increase in arboreal tree taxa and moisture-loving pollen taxa, along with a reduced representation of drought-tolerant herbs, suggests a warm and wet climate between similar to 3400 and 1600 cal yr BP (Roman Warm Period similar to 2200 to 1600 cal yr BP), similar to 1000 to 500 (Medieval Climate Anomaly), and from similar to 130 cal yr BP to the Present (Current Warm Period). In contrast, the intermittent periods between similar to 1600 and 1000 (Dark Ages Cold Period) and similar to 500 to 130 cal yr BP (Little Ice Age, LIA) were dominated by cold and drought-tolerant desert steppe vegetation. The highest concentration of pollen and fern, especially from sub-alpine tree taxa, between similar to 6100 and 5300 cal yr BP, suggests an upward shift of the tree line beyond its modern-day position, reflecting optimal climatic conditions. Conversely, during the LIA, the tree line descended to its lowest elevation in the past similar to 6100 years. The strengthened ISM episodes during the middle to late Holocene likely provided the moisture necessary for the glacier advances in the upper Bhagirathi catchment.