According to the United States Census Bureau, the township has a total area of 29.5 square miles (76.4 km²), of which, 29.0 square miles (75.2 km²) of it is land and 0.5 square miles (1.2 km²) of it (1.63%) is water.
Walker Township is bordered by Fermanagh and Fayette Townships to the north, Delaware Township to the east, Perry County to the south and Turbett Township to the west and south.