Deoxys is an alien-like bipedal Pokémon that has four Formes, each focused on a different stat. The main components that are constant for all four Formes are a dominant reddish orange color, a bluish-green face, and three bluish-green dots on its back arranged in a triangle. Typically, there is a purple stripe running down the center of its face and a purple, crystalline organ in its chest. Its white, circular eyes are set inside rectangular, black eye sockets. It is shown [[M07|in the anime]], that Deoxys may have a green crystalline organ and facial stripe.
In its Normal Forme, Deoxys has tapering legs with a segmented, vertical, blue stripe on the upper portion. The abdomen is black with vertical lines, while the majority of its skin is reddish-orange. The arms are capable of taking different forms, usually a pair of tentacles coiled in a double helix. One tentacle is the
primarily skin color, while the other is light blue. Alternately, it can form more humanoid arms with a red top and blue underside and a five-fingered hand. This Forme has a blunt protrusion with a single blue stripe on either side of its head and stubby tail.
While in its Attack Forme, its legs remain tapered. However, its blue stripes are no longer segmented and run the entire length of the leg and there is now a large spike on the knee. Two pairs of whip-like tentacles with pointed tips, one reddish-orange and one blue, replace its previous coiled, blunted tentacles. The protrusions on its head are now triangular with an additional one extending from the top of its head. Most of its reddish-orange skin has receded, revealing a striated, black chest and abdomen. Finally, its tail is now longer and more pointed.