The Nashua River flows through a scenic landscape of forests, wetlands, and fields, and supports a variety of wildlife. The boat ramp provides access to the river for kayaks, canoes, and small motorboats. 

The Nashua River main stem forms the core of the Bolton Flats Wildlife Management Area and the Oxbow National Wildlife Refuge in Lancaster, Bolton, and Harvard where it winds north through marshy areas and former agricultural fields. Pepperell Dam in east Pepperell forms Pepperell Pond, an impoundment on the river popular for trophy large mouth bass and duck hunting. The river flows north through Hollis and Nashua, Hampshire where it joins the Merrimack River. The towns of Ayer and Pepperell have wastewater treatment plants discharging directly to the main stem Nashua River. The Devens Wastewater Treatment Plant has a sub surface wastewater discharge.

Nashua River Mainstem tributaries include Bowers Brook, Catacunemaug Brook, Flints Brook, James Brook, Mulpus Brook, Nonacoicus Brook, North Nashua River, South Nashua River, Still River, Unkety Brook, and Varnum Brook.