For statistical purposes, the United States Census Bureau has defined Naalehu as a census-designated place (CDP).

Nāʻālehu is located near the southern tip of the island of Hawaiʻi at 19°3′57″N 155°35′15″W / 19.06583°N 155.58750°W / 19.06583; -155.58750 (19.065925, -155.587528)[4] in the Kaʻū District.

According to the United States Census Bureau, the Nāʻālehu CDP has a total area of 2.2 square miles (5.6 km2), all of it land.

There were 332 housing units at an average density of 153.9 per square mile (59.4/km2).

25.9% of all households were made up of individuals, and 12.1% had someone living alone who was 65 years of age or older.

Out of the total population, 22.0% of those under the age of 18 and 6.6% of those 65 and older were living below the poverty line.