Fish Creek is located in the eastern portion of the county and makes up the headwaters for a two state, three county watershed. It is the third largest watershed and accounts for 63 square miles of the county’s drainage.

The main channel begins in the east central portion of the county and drains south flowing into DeKalb County east of Hamilton. It continues to drain into the St. Joe River, which flows through Fort Wayne, Indiana, and outlets into Lake Erie, through the Maumee River.