Little is known about the foraging ecology and breeding biology of the Stygian Owl (Asio stygius robustus) across Central America. We located one Stygian Owl roost site in the Mountain Pine Ridge Forest Reserve in the Cayo District of Belize, where we collected pellets over a one-year period (n = 145; Mar 2009–Feb 2010). All identified prey items (n = 194) were passerines (69%), bats (19%), or beetles (12%). We used a proportions test and found seasonal variation in diet, with increased passerine prey consumed in the dry season (Jan–May) and increased beetle prey consumed in the wet season (Jun–Dec). This shift in diet may be influenced by temporal variation of passerine abundance and the emergence of beetles at the start of the wet season. In December 2010, we affixed an adult male Stygian Owl with a VHF transmitter, recorded regular movements using triangulation, and located an occupied nest with a single nestling in sub-montane pine forest habitat. The tagged male had a home range of 36 km2 and was documented regularly flying up to 16 km from the nest site through broad-leaved forest to hunt in agricultural habitat, while roosting and nesting only in sub-montane pine forest. The use of human-created habitats, such as agriculture, could unveil threats not previously of concern for this species (e.g., pesticide use). Our findings further our knowledge on seasonal diet for Stygian Owls and highlight distinct habitat usage for both roosting and foraging, which has important conservation implications for an understudied Neotropical owl.