NY 156 begins at an intersection with NY 443 (Helderberg Trail) in the hamlet of Berne, in the namesake town. Winding north through the town of Berne as Berne–Altamont Road, NY 156 soon crosses into the town of Knox as a two-lane rural roadway. The route soon intersects with County Route 254 (CR 254; Rock Road). After less than a block, CR 254 forks northeast along Pleasant Valley Road. Winding north through Knox, NY 156 reaches a junction with CR 255 (Gallupville Road), where it turns eastward and soon northeast along Beaverdam Creek past the Town of Knox Parklands.