In southern Ontario, Canada, the range and distribution of bats is well known, but their activity in the northeastern part of the province (north of 47°N, east of 85°W) is poorly documented. Using acoustic sampling, we documented the occurrence of six species of bats in the boreal forest of northeastern Ontario: Eptesicus fuscus (Big Brown Bat), Lasiurus borealis (Eastern Red Bat), L. cinereus (Hoary Bat), Myotis lucifugus (Little Brown Bat), M. septentrionalis (Northern Long-eared Bat), and Lasionycteris noctivagans (Silver-haired Bat). Hoary Bats were recorded more frequently than all other species. Little Brown Bats were second-most frequently recorded, and the remaining four species were encountered (mean number passes/hour) significantly less often. Our records are the most northerly for Big Brown Bats in this part of Ontario. Although the other species were expected in this area, this is the first study to identify and confirm the bats present in the boreal forest of northeastern Ontario. This new information will contribute to efforts to conserve biodiversity in the province and may inform future studies or monitoring programs associated with the spread of white-nose syndrome in Ontario.