Pinnoctopus cordiformis is identifiable by its orange-brown or purple-grey colouration; iridescent white spots are found on the arms and web.

The two can be easily distinguished by comparing a range of features: Octopus huttoni is about the size of a fist when fully mature, so is considerably smaller than the P, cordiformis; Octopus huttoni has a single row of suckers, which run up each tentacle, as opposed to Pinnoctopus, which has two rows of oppositely-arranged suckers.

[2][3] Octopus species have no bone structure, which allows easy escape from confined spaces; they also can avoid towed nets, making them difficult to study in the wild.

The eyes of an octopus are considered to be far more developed than those of many other marine species, they are primarily nocturnal and undertake a range of techniques to both escape predators and find prey.

Octopods have two different strategies in terms of spawning, the female can either hatch a few large eggs which are well-developed hatchlings and adopt the benthic promptly, or spawn large quantities of small eggs that hatch into 'planktonic free-swimming paralarvae', which have small suckers, few chromatophores, and a translucent musculature.

They generally wait by the entrances of caves or crevasses for unsuspecting fish, crustaceans, mollusks, octopuses, and other edible invertebrates.

[11][12] Pinnoctopus cordiformis has the ability to break open shellfish with its beak or by pulling it apart to eat the fish inside.

[9] Rock lobster and blue cod are two of the primary prey options for Pinnoctopus cordiformis, they get into fishing pots and devour the catch before the fisherman gets a chance.

Kupe eventually tracked it down in the Cook Strait and killed it by tricking it into holding some water containers while he struck it on the head.