Marshfield is a town in Plymouth County, Massachusetts, United States, on Massachusetts's South Shore. The population was 25,132 at the 2010 census.Marshfield is located on the South Shore, about where Cape Cod Baymeets Massachusetts Bay.According to the United States Census Bureau, the town has a total area of 31.74 square miles (82.2 km²). 28.46 square miles (73.7 km²) of it is land and 3.28 square miles (8.5 km²) of it (10.33%) is water. Marshfield is bordered by Massachusetts Bay to the east, Duxbury to the south and southeast, Pembroke to the west, Norwell to the northwest, and Scituate to the north and northeast. Marshfield is 18 miles (29 km) east of Brocktonand 29 miles (47 km) southeast of Boston.