Harmony Township is located in southeastern Beaver County at 40°36′25″N 80°13′13″W / 40.60694°N 80.22028°W / 40.60694; -80.22028 (40.607217, -80.220321).

[4] Harmony Township has four land borders, including Baden to the north, Economy to the east, Ambridge to the southwest, and the Allegheny County neighborhood of Leet Township to the south.

Across the Ohio River to the west, Harmony Township runs adjacent with Aliquippa.

As of the census[6] of 2000, there were 3,373 people, 1,439 households, and 991 families residing in the township.

28.2% of all households were made up of individuals, and 19.2% had someone living alone who was 65 years of age or older.