It extends for 10.23 miles (16.46 km) from an intersection with NY 3 by Aspinwell Corners in the town of Henderson to a junction with U.S. Route 11 (US 11) in the village of Adams.

From the early 1930s to the late 1960s, NY 178 also continued west toward Lake Ontario on what is now County Route 178.

NY 178 curves back to the southeast and intersects with CR 152 (Smith Road), where the right-of-ways merge.

From there, NY 178 begins an eastward progression through the North Country, entering the community of Roberts Corner at an intersection with CR 75 (Butterville Road).

After the interchange, NY 178 becomes known as Church Street West, crosses over a railroad line and enters the downtown portion of Adams.