The highway links U.S. Route 6A (US 6A), US 6 and US 44.

Route 128 begins at a signalized intersection with Hartford Avenue (US 6A) and Killingly Street.

The highway follows Killingly north towards a partial cloverleaf interchange with US 6 before continuing north through residential neighborhoods.

At an T-intersection with Greenville Avenue, Route 128 turns northwest before terminating at the Putnam Pike (US 44).

[1] The entire route is in Providence County.