The northwest end of NY 400 is in the southern part of Buffalo at the Thruway. The southeast end is north of the hamlet of South Wales, which is located in the town of Wales.
The northwestern terminus of NY 400 is located in the southern portion of Buffalo, where it intersects with the Thruway. Conversely, the southeastern end of the road is positioned north of the hamlet of South Wales, which lies within the town of Wales.