This study presents proxy records from lake and peatland cores obtained from the central Northwest Territories, Canada focusing on a period between 9000-4000 cal yr BP. Following the retreat of the Laurentide Ice Sheet (ca. 10,000 cal yr BP), this region was occupied by glacial Lake McConnell and meltwater routings indicate a significant northern drainage of proglacial meltwaters via Lake McConnell to the Arctic Ocean. At the northern limit of the boreal ecozone, palaeolimnological studies have documented the dynamic nature of the treeline in response to inferred warming during the Holocene Thermal Maximum. In spite of the significance of this region in the context proglacial lake drainage and boreal forest migration during the mid-Holocene, limited palaeoecological data exist from the Great Slave Lowlands and few records extend back to the period following deglaciation. This research examines eight lake and peatland records that extend from the central Great Slave Lowlands into the modern day tundra to constrain the timing and character of landscape evolution during the early to mid-Holocene in the Great Slave Lake region. A series of pollen records are presented to examine boreal forest migration and the treeline mobility, whilst a programme of radiocarbon dating provides new insights into the rates of peatland initiation. Quantitative temperature reconstructions have been derived from fossil chironomid assemblages. The chironomid-inferred summer air temperatures represent the first palaeotemperature reconstructions for the central Northwest Territories that span the early to mid-Holocene and provide new insights into ecosystem responses to climate amelioration in the boreal zone. These results add to the recent theories regarding treeline advance in Europe and provide long-term insights into the relationship between vegetation cover, natural disturbances and climate on ecosystem characteristics.