Omnimon is a massivel tall white knight Digimon covered in overlapping plates of armor made of Chrome Digizoid. His left shoulder is armored with the Brave Shield, and his right is based on MetalGarurumon's standard shoulder armor. His right hand is made up of MetalGarurumon's head, and conceals his primary long-range weapon, the Supreme Cannon. In turn, his left hand is made up of WarGreymon's helmet, and wields the Transcendent Sword. In the center of his chest is symbol that is composed of half of the Crest of Friendship and half of the Crest of Courage. A large cape drapes behind him.
In Merciful Mode, empowered by the rest of the Odaiba Eight's Digimon partners in their Mega Level forms, he takes on an almost purely blue and white appearance. In this form, in place of a cape, two massive feathered wings appear behind him, and the Transcendent Sword is reshaped to appear as a massive katana rather than as a double-edged blade.