[4] New Windsor is located on the eastern edge of Mercer County at 41°12′6″N 90°26′38″W / 41.20167°N 90.44389°W / 41.20167; -90.44389 (41.201643, -90.443996).

According to the U.S. Census Bureau, the village has a total area of 0.44 square miles (1.1 km2), all land.

Pope Creek and the Edwards are west-flowing direct tributaries of the Mississippi River.

The racial makeup of the village was 98.75% White, 0.28% Native American, 0.28% Asian, and 0.69% from two or more races.

28.0% of all households were made up of individuals, and 18.9% had someone living alone who was 65 years of age or older.