SR 108 starts at an intersection with SR 8 west of Downtown McCleary. From the intersection, the road briefly goes north before turning east onto "Simpson Avenue" into Downtown McCleary. Simpson Avenue goes into McCleary and comes to a 3-way intersection with "Main Street" at Beerbower Park. SR 108 then turns onto "Main Street" and becomes "Summit Road", passing Lake Clara before leaving Downtown McCleary. After passing Hillgrove, the highway enters McCleary Junction and turns northeast to parallel the Puget Sound and Pacific Railroad.