Route 105 begins at U.S. Route 6 in Marion. The highway crosses over I-195 less than a mile into its journey. The highway winds in a westerly direction through Rochester. When the highway enters Long Plain village in Acushnet, the only town in Bristol County on the route, Route 105 turns in a northerly direction. The highway returns into Rochester and enters Lakeville between Little Quittacas and Great Quittacas Ponds. Route 18 joins Route 105 for a 2.7-mile (4.3 km) concurrency, running along the western shore of Assawompset Pond. Route 105 then shoots off in a northeasterly direction into Middleborough through the town’s center and, after its intersection with U.S. Route 44, turns in a northerly direction through East Middleborough, going past Oak Point along the way. The highway ends at Route 106 in Halifax west of the town's center.