Brainstorm has a light orange crab-like appearance with pincers for hands. He can open his skull plates at will to reveal his huge, corrugated brain, which is pink in color.

In Alien Force and Ultimate Alien, Brainstorm had six legs and wore a silver and black neck brace with the original Omnitrix/Ultimatrix symbol on it.

In Heroes United, Brainstorm looked mostly the same except his shell was a more vibrant orange and his skull plates were black.

In Omniverse, Brainstorm has a black loincloth with a green stripe in the center of it on the bottom of his body. He also has a black stripe in the center of his head with a green stripe running across it. He now has four legs instead of six, and each leg has a single joint instead of two, with a black stripe on each one. The spines on Brainstorm's face and forehead are now longer, and his eyes connect to a large black strip that extends around his forehead. He also has two spikes on each elbow, and he wears the Omnitrix symbol on a white and green neck brace.