[3] The river's headwaters are near Survey Pass in the Endicott Mountains on the north slope of the central Brooks Range, and the river mouth is south of Angoyakvik Pass.

[4] The direction of the headwaters stream is northwest at first, then sharply northeast before April and Easter creeks enter from the right slightly north of the North Slope Borough boundary.

[4] Major tributaries of the Killik are April and Easter creeks, as well as the Okokmilaga.

The main stem flows down a U-shaped glacial valley containing lakes, sand dunes, lateral moraines, and alpine tundra.

The Killik is fed largely by precipitation and snow melt, and hence its waters are relatively clear of the sediment that characterizes glacial streams.