Wonderweiss's personality is very childlike and possibly autistic; for example, when sent on a mission to kill, he instead played around with a dragonfly. He only has two teeth visible when smiling. He shows some hostility, firing a defensive Bala blast at one point. Wonderweiss displays a higher level of hostility by stabbing Ukitake through the chest without any warning or provocation. Despite his childlike demeanor, he also displays some compassion by freeing Tia Harribel. Wonderweiss does not speak in coherent sentences, only saying a few syllables at a time such as an infant would.