Some taxonomic authorities, including the International Ornithologists' Union, place this species in the genus Leucocarbo.

The New Zealand king shag was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[2] Gmelin based his description on the "carunculated shag" that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds .

[3] The New Zealand king shag is now one of 16 species placed in the genus Leucocarbo that was introduced in 1856 by the French naturalist Charles Lucien Bonaparte.

[4][5] The name Leucocarbo combines the Ancient Greek leukos meaning "white" with the genus name Carbo introduced by Bernard Germain de Lacépède in 1799.

[5] It is a large (76 cm long, 2.5 kg in weight) black and white cormorant with pink feet.

[8] New Zealand king shags can be seen from the Cook Strait ferries in Queen Charlotte Sound opposite the beginning of the Tory Channel.

[10] The most commonly observed breeding colonies are Duffers Reef, North Trio Island (Kuru Pongi), White Rocks, and Tawhitinui.

[8] The king shag breeding season spans from February to April, with eggs being laid as late as May.

King shags show strong nesting site fidelity, returning to the same colony to breed on repeated years.

Colonies on the outer edge of the Marlborough Sounds saw higher mortality rates, likely due to lack of shelter against weather.

[13] Individual king shags show a wide range in variation of diving durations and depths.

Due to the increased depth, male king shags tend to dive for longer durations than females.

King shags typically consume their prey underwater, but there have been multiple observations of individuals surfacing carrying flatfish.

Remnants of octopus, crab, and lobster have been found within the pellets of king shags, but it is unlikely that the birds consume them directly.

There was worry that the space used for mussel farming would reduce foraging grounds for king shags, but the populations are not affected meaningfully by current aquaculture.

It is thought that the structure of mussel farms, with their floating buoys, offer temporary spots to roost and preen before returning to the colony.

[8] Fishing and travel through the Marlborough Sounds by boat are considered the largest forms of disturbance to king shags.