The Scantic River's tributaries rise in the towns of Hampden, Wilbraham, East Longmeadow and Monson in Massachusetts, and in Stafford and Somers, Connecticut, forming the river in the town of Hampden, Massachusetts southeast of Springfield. The Scantic flows southwest for 40.6 miles (65.3 km) through the towns and communities of Hampden, Massachusetts; Somers, Somersville, Scitico, Hazardville, Enfield, East Windsor, Broad Brook, Scantic, South Windsor, and East Windsor Hill, Connecticut, until joining the Connecticut River ( ) near the East Windsor Hill community, part of South Windsor.
There are two areas named after the river. One is a small community, part of East Windsor. The other is in the southeast section of Hampden, near the corner of Scantic Road and Rock-A-Dundee Road.
The state of Connecticut is working to form a state park surrounding the Scantic River in the towns of Somers, Enfield, East Windsor, and South Windsor. Two areas that are proposed for public park areas are the Scantic River State Park at Powder Hollow in Enfield and the Scantic River State Park at Trolley Crossing just south of Broad Brook where the planned route of the Connecticut Trolley Museum's main line crosses the river.
Among things named after the river are several roads, the Scantic River Valley YMCA, the Scantic River Artists, the Scantic River Watershed Assn., and many others.