NY 173 begins at an intersection with NY 31 in Ionia, a hamlet within the town of Van Buren. The route heads southeast, intersecting several county roads as it proceeds through a rural, marshy area of Onondaga County as Warners Road. It crosses over the New York State Thruway (Interstate 90 or I-90) on its way into the hamlet of Warners, where it briefly follows Canton Street and crosses the CSX Transportation-owned Rochester Subdivision rail line before becoming Warners Road once again as it follows the railroad east out of the community and into the town of Camillus.