Westchester Township is one of the twelve townships in Porter County.  It is bounded on the north by Lake Michigan, on the east by Pine Township, on the south by County Road 1100 North, and on the west by Portage Township.  It consists of part of Chesterton, part of Portage, Burns Harbor, Porter, and Dune Acres, and unincorporated areas of land as well.

There are 20,635 people, according to the census of 2020. It encompasses 35.85 square miles, with land being 32.05 square miles and water being 3.8 square miles.

Westchester Township is within the Great Lakes Watershed, which eventualy empties into the Atlantic Ocean.  Sand dunes are the most notable geographic feature in Westchester Township.  They are hills of sand that are approximately 50-100 yards back from the water, and can range from three-quarters of a mile to a mile in width.