According to the United States Census Bureau, the town has a total area of 47.8 square miles (123.7 km²), of which, 44.3 square miles (114.7 km²) of it is land and 3.5 square miles (9.1 km²) of it (7.35%) is water. Drained by Seven Mile Brook, Vassalboro is bounded on the west by the Kennebec River.

The town is crossed by U.S. Route 201, U.S. Route 202, Maine State Route 3, Maine State Route 9, Maine State Route 32, Maine State Route 100. It borders the towns of China to the east, Augusta to the south, Winslow to the north, and across the Kennebec River, Sidney to the west.

Vassalboro Area Code is 207

• Town of Vassalboro, ME - 682 Main Street, PO Box 129, North Vassalboro Maine 04962
  Telephone: 207-872-2826 Fax: 207-872-5414
• Vassalboro Public Library - 930 Bog Road / PO Box 62, East Vassalboro ME 04935
  Phone: 207-923-3233