Kasilof River starts at the outlet of Tustumena Lake on the Kenai Peninsula and flows generally northwest for 17 miles (27 km) through the Kenai Lowland to Cook Inlet, draining a watershed of 93,275 acres (37,747 ha), about 51 miles (82 km) north-northeast of Homer and 13 miles (21 km) south-southwest of Kenai, Alaska.