Long-term streamflow time series were analysed to provide evidence of climate change in the Hudson Bay region. We also investigated whether relationships exist between streamflow and proximal temperature and precipitation time series. The Mann-Kendall test for trend reveals an earlier occurrence of the spring peak flow in three rivers flowing into southern Hudson Bay, with a statistically-significant warming trend for spring temperature. In the northwestern Hudson Bay region, precipitation has significantly increased in all seasons, resulting in increasing trends in the discharge of the Kazan River. In contrast, a decrease in river discharge was detected in central Manitoba, because of warmer temperatures and less abundant rainfall. On the east side of Hudson Bay, statistically-significant streamflow trends were detected for individual months, but temporally and spatially coherent patterns could not be identified. This study of the Hudson Bay streamflow provides evidence of climate change using streamflow and climate data in the Hudson Bay region over the past century. The climate change signal is not spatially uniform and is obscured when the Hudson Bay basin is treated as a single large region.