Peatlands are known sources of the bioaccumulating neurotoxin methylmercury (MeHg) and sinks for inorganic mercury. Wildfires alter the cycling of mercury by changing biogeochemical processes within peatlands and emission of mercury into the atmosphere. Climate change is intensifying fire regimes, increasing severity of wildfires and uncertainty about the impacts of wildfires on peatland mercury cycling, particularly changes in mercury cycling years after wildfires. The objective of this study was to investigate the mobilization of MeHg and total mercury (THg) five years post-fire in twelve burned and unburned peatlands in a hemi-boreal rock barren landscape. The Parry Sound #33 wildfires burned >11,000 ha in 2018. The burned sites were separated by burn severity measured as the depth of burn (low, medium, high). In 2023 (April to November), we sampled water chemistry (Hg speciation, trace metals, dissolved organic matter concentration and composition) and water discharge. We found high burn severity had the lowest discharge values (L/day), while having the highest MeHg peatland productivity (ng/m2/day) indicating possible higher release of MeHg in the outflow compared to other sites. In the fall increasing burn severity increased the percentage of total mercury present as methylmercury, while runoff sulfur concentrations decreased, indicating that the increased percentage of methylmercury may be due to solubility changes rather than net mercury methylation. Given that wildfire burn severity is increasing due to climate change and seemingly prolonged impact of wildfires on methylmercury export, we suggest wildfires have long-term detrimental impacts on water quality in downstream aquatic ecosystems in this landscape.