Originally occupied by Lenape Native Americans, Willistown Township was part of the 50,000 acres (200 km2) Welsh Tract surveyed for William Penn in 1684.

The first roads in Willistown Township were Native American trails.

[3] According to the U.S. Census Bureau, the township has a total area of 18.2 square miles (47 km2), all land.

Willistown Township is a part of the suburban area west of Philadelphia known as the Main Line.

At the 2010 census, the township was 92.0% non-Hispanic White, 2.1% Black or African American, 3.6% Asian, and 0.8% were two or more races.

20.9% of all households were made up of individuals, and 7.7% had someone living alone who was 65 years of age or older.

Pennsylvania Route 3 follows West Chester Pike along an east–west alignment across the southern portion of the township.

Finally, Pennsylvania Route 926 starts at PA 3 and heads southwest along Street Road in the southern corner of the township.