The Yellow Rail (Coturnicops noveboracensis) is a secretive marsh bird of conservation concern in Canada. However, the status of this species in northern boreal regions remains largely unknown given uncertainty about population abundance and distribution. This knowledge gap is mainly due to limitations of traditional survey methods to detect this species. In this study, avian point count data collected from autonomous recording units and augmented by detections from a machine-learning recognizer were used to generate a species distribution model to provide habitat-specific density estimates and population size estimates for Yellow Rail breeding in the Edéhzhíe Dehcho Protected Area, Northwest Territories. This protected area is ∼150 km beyond the currently established northern range limit. A large population estimated at 906 (± 146) pairs was discovered. Yellow Rail were found at high densities in marshes (0.063 ± 0.004 males/ha), but were also observed in fens and bogs, albeit at much lower densities (0.003 ± 0.002 males/ha and < 0.001 ± 0.002 males/ha). Our results suggest both the range and the population size of Yellow Rail are much larger than currently reported. Further studies are required to provide better population size and distribution estimates to conserve this species at risk in Canada.