Large and bulky, Knifehead is a heavily built Kaiju. Its most notable feature is the long and broad, sharp-ended nose that could easily cut through the armor of a Jaeger. Atop the center of its head resides a blowhole that forcefully expels air whenever it resurfaces from the water.[3] It has large, shell-like armor on its back while the rest of its body is similar to that of a goblin shark in appearance.

Knifehead possesses two large, dominant arms and two smaller, secondary arms protruding from its belly. Its large arms each have three-clawed digits, the middle digit being significantly larger. It also has a tail. Bright yellow lines run across its body, with the rest of its body being a dark grey. Its eyes and the interior of its mouth, however, glow blue.

Like Slattern, Trespasser, and Scunner, Knifehead's primary forearm bones have a fleshless gap between them, looking like two fused arms ending in three-digited claws. Knifehead is the largest Category III Kaiju recorded so far, topping fellow Category III Kaiju Yamarashi's record.