Pewaukee is located at 43°4′N 88°15′W (43.0614, -88.2495). It is located in the Lake Country area of Waukesha County.
According to the United States Census Bureau, the city has a total area of 21.15 square miles (54.78 km2), of which, 19.50 square miles (50.50 km2) is land and 1.65 square miles (4.27 km2) is water.
