Katsuki is a very crude, violent, arrogant, and aggressive person. Having an attitude reminiscent of a teenage delinquent, Katsuki tends to come off as very anti-heroic, if not downright villainous. This problematic behavior goes all the way back to his early childhood days, when he was known to bully a young, Quirkless Izuku Midoriya. However, after being accepted into U.A. High and experiencing several personal defeats, one of them even coming from Izuku, Katsuki has gradually changed into a less antagonistic person, albeit still retaining a lot of his unpleasant traits.

Brutal and bloodthirsty, Katsuki smiles eerily when finding himself in the middle of a battle. His personality reflects his fighting style: mercilessly assaulting the opponent and having no regard for nearby objects, merely destroying them with his power. Despite this, he's quite talented in fighting, using his Quirk in various ways besides attacking. He's also very intelligent, being capable of strategic planning and holding some of the highest grades in his class, to the point that some even consider him a natural genius.