It runs from the Connecticut border in Wales north to an intersection with Massachusetts Route 9 and Massachusetts Route 67 in the town of West Brookfield.

The highway continues south of the state border as Connecticut Route 19.

Route 19 in Massachusetts begins when Route 19 in Connecticut crosses from Stafford, Connecticut, into Wales, Massachusetts.

Route 19 continues north out of the town and heads due north, eventually crossing into the town of Warren in Worcester County.

Just after crossing into Warren, Route 19 passes underneath the Massachusetts Turnpike (I-90) without an interchange.