The road runs from the Massachusetts border at Hollis to North Hampton on the Atlantic shore.

The eastern terminus of NH 111 is at the junction with Ocean Boulevard (New Hampshire Route 1A) in North Hampton.

Eastbound NH 111 continues in a mostly northeasterly direction along Runnels Bridge Road, crossing the Nashua River about 1/2 mile from the border, and passing the Overlook Country Club.

Going through an industrial part of East Nashua, still following the south bank of the Nashua River, NH 111 crosses the twin-span Taylor Falls/Veterans Memorial bridges over the Merrimack River (known locally as the Hudson Bridge) into the town of Hudson.

Passing through an industrial area of eastern Hudson, NH 111 enters Windham shortly before crossing Mammoth Road/NH 128.

After intersecting with Rockingham Road/NH 28 the route turns to a more northerly direction, and crosses into the extreme northern part of Salem.

Leaving Exeter, NH 111 crosses a few dozen feet of the southern corner of Stratham, providing access to a small industrial park.

The western segment of NH 111A is a 4.935-mile-long (7.942 km) northeast–southwest loop road in Hollis and Nashua in Hillsborough County.

The western terminus is at NH 111 approximately 0.8 miles (1.3 km) north of the Massachusetts state line in Hollis.

The southern, officially western, terminus is in the town of Pelham at New Hampshire Route 128 (Mammoth Road) approximately 0.5 miles (0.80 km) north of the Massachusetts state line.

The northern, signed eastern, terminus of the highway is in the town of Windham at NH 111 between Cobbetts Pond and Canobie Lake.

The eastern segment of NH 111A is a 15.024-mile-long (24.179 km) northeast–southwest highway between Danville and Exeter in Rockingham County.