Katsuki is a young man of average height, with a slim, muscular build, and a fair skin tone. He has short, spiky, ash-blond hair with choppy bangs that hang over his eyebrows. His eyes are sharp and bright red in color.

At school, he wears the standard U.A. uniform without the customary red tie. Underneath his blazer, he wears a white collared shirt with the top few buttons undone. His pants are worn loosely, causing them to sag at his ankles, despite him wearing a belt with them.

His hero costume is composed of a tight, black, sleeveless tank top, with an orange “X” across the middle, forming a v-neck. There are two dots along the left line of his collar, indicating the support company that designed his costume. His costume also has a metallic neck brace worn with rectangular ends that have three holes on each side. His sleeves reach from within his large grenade-like gauntlets to his biceps. His belt, which also carries grenades, holds up his baggy pants with knee guards, below which he sports black, knee-high combat boots with orange soles and eyelets. His mask is jagged and black, and as it goes around his eyes, a large, orange-rimmed flare shape protrudes from each side.