The head, underparts, tail, and the small "mirrors" at the wing tips are white.

Juveniles have dull legs, a black bill, a dark band in the tail, and an overall grey-brown plumage densely edged whitish, but they rapidly get a pale base to the bill and largely white head and underparts.

The kelp gull is a rare vagrant to the United States, with the first record in 1989 on Chandeleur Islands in Louisiana.

They have interbred with American herring gull on these islands, leading to intermediate birds that may backcross to one another.

They gather on landfills and a sharp increase in population is therefore considered as an indicator for a degraded environment.

[10] The kelp gull uses its powerful beak to peck down centimetres into the skin and blubber, often leaving the whales with large open sores, some of which have been observed to be half a meter in diameter.

[11] At rocky sites along the Southern African coast, such as at Boulders Beach in Cape Town, kelp gulls (Larus dominicanus vetula) can be seen picking up shellfish and repeatedly flying up several meters and dropping them onto the rocks below in order to break them open.