The CDP is in the center of the town of Henniker, primarily on the north side of the Contoocook River but with a small portion on the south side, comprising the campus of New England College.

According to the U.S. Census Bureau, the Henniker CDP has a total area of 1.4 square miles (3.7 km2), all of it recorded as land.

As of the census of 2010, there were 1,747 people, 556 households, and 269 families residing in the CDP.

34.7% of all households were made up of individuals, and 11.5% were someone living alone who was 65 years of age or older.

547 people (31.6% of the population) lived in group quarters such as dormitories, rather than households.