Globally, the severity of wildfires is predicted to continue to rise due to climate change. Although fire is an important natural disturbance, it is unknown how changes in the fire regime affect forest biodiversity, including the bat community. Fire impacts insectivorous bats by changing foraging habitat, insect communities, and roosting opportunities. Our objective was to determine the effect of an extreme-severity wildfire on the bat community in Waterton Lakes National Park (WLNP), Alberta, in the Canadian Rocky Mountains. The Kenow wildfire burned 38% of WLNP in 2017. We hypothesized that the fire had a positive effect on all bat species in the study area, driven by increased foraging availability in the burned areas, coupled with the local unburned areas that provided fire refugia. We examined WLNP bat activity using acoustic detectors to record bat echolocation calls at thirteen sites for three years before and three years after the wildfire. We used negative binomial generalized linear mixed models parameterized using a before-after control-impact design. Our results indicate that the response to the fire depended on the bat species. 40 kHz Myotis responded positively to the wildfire. Compared to pre-fire activity, 40 kHz Myotis activity increased in burned areas (pre-fire mean 34.9 ± 5.4 SE passes/night versus 70.1 ± 17.5 post-fire) and decreased in unburned areas (pre-fire 132.0 ± 27.6 passes/night versus 123.0 ± 22.7 post-fire), suggesting that for foraging, they moved from unburned to burned areas post-fire. The big brown bat (Eptesicus fuscus) and silver-haired bat (Lasionycteris noctivagans) species group was primarily negatively affected, with fewer passes post-fire compared to pre-fire in both burned (pre-fire 18.2 ± 4.5 passes/night versus 12.3 ± 2.5 post-fire) and unburned areas (pre-fire 44.6 ± 6.4 passes/night versus 34.9 ± 6.1 post-fire). However, activity increased in the burned sites immediately post-fire, and then decreased in years two and three. Hoary bat (Lasiurus cinereus) activity was negatively affected by the wildfire in all years, and in both burned (pre-fire 5.0 ± 0.8 passes/night versus 0.7 ± 0.2 post-fire) and unburned sites (pre-fire 17.3 ± 3.1 SE passes/night versus 6.7 ± 1.2 post-fire). We suggest that the differences among species/species groups were primarily due to changes in foraging opportunities and differences in prey selection. Additional acoustic monitoring would elucidate the long-term effects of the fire on the bat community and provide insight into the adaptability and resilience of insectivorous bats to climate change driven wildfires.