The CDP is in the center of the town of New Boston, on both sides of the South Branch Piscataquog River.

The CDP extends west past Briar Hill Road, south down Route 13 to its crossing of the South Branch, east to Molly Stark Lane and Hilldale Lane, and north up Route 136 to Beard Road.

[3] New Hampshire Route 13 passes through the center of the community, leaving to the northeast down the South Branch valley along River Road, and leaving to the south along Mont Vernon Road.

New Hampshire Route 136 has its eastern terminus at Route 13 and leads west 7 miles (11 km) to Francestown, while New Hampshire Route 77 has it southern terminus at the same junction with NH 13 but leads north 9 miles (14 km) to Weare.

[4] Via the South Branch of the Piscataquog, New Boston is part of the Merrimack River watershed.