Canada�s boreal zone is a complex mosaic of forests, wetlands, streams and lakes. The pool of carbon (C) stored in each of these ecosystem components is vast, and significant to the global C balance. However, dissolved organic carbon (DOC) pools and fluxes are heterogeneous in time and space, which contributes to uncertainty in predicting how a changing climate will affect the fate of C in these sensitive ecosystems. The objective of this project was to investigate factors controlling spatial variability in soil and stream DOC concentrations, and sensitivity of these patterns to climatic factors. We conducted a detailed examination of soil water and stream DOC export from a 320 ha boreal forested catchment in northwestern Ontario, Canada. Long-term stream discharge and DOC records were coupled with soil and soil leachate samples. Soil C stocks were well predicted by spatial characteristics, including soil depth and bulk density. Soil water DOC quantity and quality were variable in response to hydrological and climatic conditions, particularly following prolonged drought events. The proportion and location of wetlands within the catchments were good predictors of DOC concentrations, but DOC optical metrics varied depending on hydrological condition, suggesting DOC sources to streams and lakes are sensitive to climate-driven changes in flowpaths. As summer temperatures increase and summer droughts become longer and more intense, understanding controls on variability in catchment DOC sources and transport is critical for predicting changes in stream dynamics.