Armaldo is a bipedal, amphibious Pokémon, somewhat resembling a mantis shrimp and covered with thick, heavy-duty plates.

It is mainly coloured blue, with accents of yellow, black, white and red. Additionally, Armaldo's eyes, like its pre-evolution, extend from the sides of its head. However, they are not beady and instead oblong in shape. Armaldo also retains the black pattern on its head present in its pre-evolution. Armaldo has a long neck, with the lobes that were present on the sides of Anorith's body there, although there are now three pairs instead of four. Armaldo has a yellow lower jaw, and a continuation of the yellow coloration on the rims of the armour on its underside. The yellow patterning encircles the holes on the armour of the underside out of which Armaldo's blue-and-black-tipped, segmented blade-like arms extend. The yellow rim on the shell underside culminates on Armaldo's lower belly, although there is also yellow rimming on the fin-like, triangular "wings" on Armaldo's sides. Armaldo's legs are thick, with black-colored knees and two toes. Armaldo's long tail is similar to that of Lugia's in shape, although blue with black fins.