Wildfires are becoming more frequent, widespread, and severe in Alaska’s boreal forest ecosystem, but their effects on rivers and salmon populations are not well understood. Do wildfires increase water temperatures over the following years or decades? Do burned watersheds supply juvenile salmon with improved or diminished invertebrate food supplies? How do such changes ultimately affect salmon growth rates, which can influence future marine survival? We addressed these questions using remote sensing, downscaled climate models, and a spatially explicit riverscape bioenergetics approach calibrated with field water temperature, fish growth, and diet data for a ~20,000 km2 boreal stream network in interior Alaska. We used a BACI design to compare land surface temperatures (LST) in tributary catchments as a function of fire history, vegetation composition, and elevation for 15 years post-fire. Model predictions were compared to measured thermal regimes from tributary streams (catchment area range: 12 to 150 km2) with varying fire histories monitored from 2014 to 2022. We found that burn scars were 2-3˚C warmer on average than nearby reference areas in the five years following a fire and remained 1˚C warmer after 15 years. Tributary stream temperatures predicted from LST indicated that fires led to a > 1˚C stream temperature increase during midsummer and generally increased juvenile salmon growth in bioenergetics simulations. We found that the magnitude of wildfire effects on stream temperatures increased from the recent historic period to mid- and late-century future periods in our simulations. Our model predicted that the cumulative warming effects of climate change and wildfires will increase juvenile salmon growth potential in most cases by mid-century. These findings provide insights into the effects of wildfire on watersheds and salmon in the boreal forest ecoregion. We discuss implications of changing fire regimes for fisheries resources and practical considerations for land managers and communities.