New Zealand fur seals are sexually dimorphic, with adult males reaching 1.3 times the length and 3 times the weight of adult females. The muzzle is moderately long, flat, and tapers in width and depth to a bluntly-pointed nose.  The rhinarium is fleshy, wide, and especially in males, droops down slightly at the end.  In adults, the vibrissae are cream to white and medium to long.  The ear pinnae are long and prominent.

Adult males have a mane of elongated, coarse guard hairs covering the greatly enlarged neck, chest, and shoulders, which extends to the nape and the top of the head.  The crown is somewhat rounded, due to the modest sagittal crest, and there is a slight forehead. The canine teeth of adult males are larger and thicker than those of females.  Adult females, subadults and juveniles have a flatter head with a minimal forehead.

 The fore flippers have a dark, sparse, short fur that extends beyond the wrist onto the middle of the dorsal surface of the flipper in a “V” pattern that does not reach the rounded tip.  The rest of the dorsal surface, and the palms of both fore flippers are covered with a hairless black leathery skin.  The first digit is the longest, widest and thickest, and unlike most otariids has a relatively straight, rather than posteriorly curving, leading edge, giving the flipper a triangular look.  Digits 2-5 are successively shorter.  There is a small opening in the skin at the end of each digit for a claw that is usually reduced to a vestigial nodule, and rarely emerges above the skin.  The claw openings are set back from the free edge of the flippers by cartilaginous rods that extend the length of each digit, and expand the size of the flippers.

The hind flippers have dark, short, sparse hair covering part of the proximal end of the flipper, and the rest of the dorsal surface, and the entire sole is covered in black leathery hairless skin.  The hind flippers are long and each digit has a cartilaginous rod that adds a flap-like extension to each toe.  The bones of the three central toes terminate at the position of the small nails that emerge through the skin on the dorsal surface, set back from the end of the flipper.  The claws of digits 1 and 5 are vestigial like the claws on the fore flippers, and may or may not emerge from small openings set back from the end of the flaps.  All of the flaps at the end of the flipper are of relatively equal length.  The first toe or hallux and the fifth toe are somewhat wider than toes 2–4.

Adults are dark olive brown or gray brown above and paler below.  The muzzle is variably paler, gray to rusty tan on the end, in the mystacial area, and around the line of the mouth.  The ear pinnae and the area around their insertions are also paler.  Adult females are paler on the undersides than males, and are also pale from the lower sides of the abdomen to the chest and neck.  Pups are blackish, except for a pale muzzle and undersides.  They molt to adult pelage at 2-3 months.

There is some variation in weights of adult males in the literature.  Some ranges are up to a maximum of 250 kg, others to 200 kg.  The largest male weighed at the Open Bay Islands of New Zealand was 154 kg.  Adult males 8-12 years old had a maximum weight of 124 kg.  Adult males are up to 2 m long.  Adult females are 1.5 m and 30-50 kg.  Pups average 3.3-3.9 kg and 40-55 cm at birth and males average 14.1 kg and females 12.6 kg around weaning at 290 days old.

The dental formula is I 3/2, C 1/1, PC 6/5.

New Zealand fur seals share their range with five other otariids: Antarctic, Subantarctic, and Australian fur seals, and New Zealand and Australian sea lions.  Shape of the head and muzzle, presence of a dense underfur, coloration, size and prominence of ear pinnae, and length of the toes on the hind flipper readily distinguish New Zealand fur seals from both sea lions.

Australian fur seal bulls are larger and heavier but less stocky with a long head and wider, tapering, but blunter muzzle with a large rhinarium that extends well beyond the mouth.  The leading edge of the fore flipper curves posteriorly, as opposed to the straighter edge of the fore flipper of the New Zealand fur seal.  The guard hairs of the mane are longer, and the neck and shoulders much more massive and muscular than on New Zealand fur seal males.  Males are pale gray brown to dark gray brown, but paler than New Zealand fur seal bulls.  Females are fawn to medium gray brown, paler below and on the neck, and paler above than female and subadult New Zealand fur seals.

Distinguishing New Zealand fur seals from Antarctic fur seals is more difficult due to similar size, shape and coloration.  Note the straighter leading edge of the fore flipper in New Zealand fur seals than in Antarctic and Subantarctic fur seals.  Adult male Antarctic fur seals have extensive light grizzling on the mane, are darker than adult male New Zealand fur seals being dark brown to very dark gray, have a wider and shorter muzzle, smaller rhinarium, and steeper forehead.  Separating females, subadults and juveniles out of range or isolated is problematic.

Subantarctic fur seals are uniquely colored.  The back and rump of adult males is dark gray to brownish black, and the chest and neck through the muzzle, face and area around the eyes are cream with yellow to orange shading.  The ear pinnae are short, mostly bare skin and dark, and attach in the dark pelage of the upperparts.  There is also a tuft of longer pale fur in the dark crown above the eyes and behind the dark forehead.  Although the adult male is enlarged and thick in the shoulders and neck, he does not have a mane.   Adult females have similar coloration to the males, but have less well-defined pale facial markings that can be shaded with dull yellow orange to light brown.  In both sexes the top of the fore flippers is darker as is the area where the flippers attach to the sides.  The underside of the abdomen is dark ginger to reddish brown.  The fore flippers and hind flippers are proportionately short and wide.

New Zealand fur seals are distributed in two geographically-isolated and genetically-distinct populations.  In New Zealand, they occur around both the North and South Islands, with small breeding colonies on the north, and larger colonies on the west and southern coast and islands of the South Island, and on all of New Zealand's sub-Antarctic islands.  They are less common off the North Island, with no colonies, but occur as far north as the Three Kings Islands.  They are present, but do not breed, on Macquarie Island in April and May.

A separate population occurs in the coastal waters and on the offshore islands of southern and western Australia, from just east of Kangaroo Island west to the southwest corner of the continent in Western Australia.  Vagrants have been recorded in New Caledonia, and from a bone in a 14^th century archaeological site in the Cook Islands.

New Zealand fur seals prefer rocky habitat with shelter, and locations more exposed to wind and weather. They will also readily enter vegetation.  Little is known of distribution at sea, although they seem to prefer waters of the continental shelf and slope, and are found widely in waters over the Campbell Plateau, south of New Zealand.