The Government of Canada has committed to planting two billion trees across the country by 2031 in an effort to sequester carbon to combat climate change. We have little knowledge on how Canada's watersheds will respond to extensive tree planting efforts as part of this program, as most research on streamflow response to afforestation is from semi-arid environments with no snow. We used forest cover and hydrologic data from catchments in the Sudbury area to assess how afforestation may have affected streamflow in a snow-influenced region. In the early 1970s, much of the Sudbury area was devoid of forest vegetation due to historical mining practices. Extensive regreening efforts starting in 1978 have resulted in over 10 million trees being planted in the region. Coniston Creek (catchment area of 80 km²), which is gauged by the Water Survey of Canada, had forest cover increase by 19% and barren land decrease by 23% between 1984 and 2019 due to regreening efforts. We hypothesized that an increase in forest cover of this magnitude would be associated with a decrease in streamflow due to increased evapotranspiration. Using a variety of hydrologic change detection approaches, we found that summer streamflow may have increased in response to afforestation; however, the results are highly uncertain due to lack of robust reference catchments, confounding influences of both climate variability and non-afforestation land cover changes, as well as data limitations. We recommend more targeted experiments to investigate afforestation effects on hydrology in a Canadian context.