WIS 155 begins at a junction with WIS 70 in the community of St. Germain. From here, the highway heads north through a forested region with many lakes; the route lies entirely within the
Northern Highland-American Legion State Forest. The route passes through the
Town of St. Germain to the east of
Big Saint Germain Lake before curving to the northwest to bypass
Lost Lake. After crossing a small creek, the highway turns west toward a junction with County Highway C. WIS 155 turns north at the junction and continues through a populated area south of Sayner. The route curves northwest into Sayner, entering the
Town of Plum Lake as it does so. The highway intersects CTH‑N in Sayner, and the two highways run
concurrently through Sayner. The routes run through a mixed residential and business district, passing the Vilas County Historical Museum and the Plum Lake Library. WIS 155 ends in northern Sayner at another junction with CTH‑N, which continues to the west;
Plum Lake lies to the north of the terminus. ==History==