NY 249 begins at a junction with NY 5 (the Seaway Trail / Erie Road) and County Route 34 (CR 34; Lotus Point Road) in the village of Farnham, located in the town of Brant. NY 249 proceeds eastward away from NY 5 as a two-lane residential road, crossing east through Farnham as Commercial Street. The route crosses under tracks owned by CSX Transportation. After the tracks, NY 249 darts southeast, then east through Farnham as a two-lane residential roadway, crossing the eastern village line. In Brant, NY 249 drops the Commercial Street moniker in favor of Brant–Farnham Road, crossing an at-grade intersection with US 20 (Southwestern Boulevard).