The CDP is bordered to the southwest by the New York State Thruway and to the south by the Albany County line.

Neighborhoods in the CDP include (from west to east) South Schenectady, Coldbrook, and Carman.

According to the United States Census Bureau, the Rotterdam CDP has a total area of 6.9 sq mi (18 km2), all land.

As of the census[6] of 2000, there were 20,536 people, 8,492 households, and 5,876 families residing in the CDP.

27.0% of all households were made up of individuals, and 14.3% had someone living alone who was 65 years of age or older.