The 19.5 miles (31.4 km) portion from Skilak Lake downstream to the Sterling Highway bridge near Soldotna is known as "Middle River".

The final 21 miles (34 km) from the bridge to the mouth at Cook Inlet is known as the "Lower River", where the flow is much gentler.

The world record king salmon, which weighed about 44 kg (97 lb), was caught in the Kenai River in 1985.

A typical king in the second run, beginning in mid-July, weighs 40–85 pounds (18–23 kg), with considerably larger specimens not uncommon.

In recent years, the king salmon fishery has been closed or heavily restricted due to low returns of fish.

[9] The September run is favored by local anglers due to the larger size of the silver salmon.