Tanjiro looks remarkably similar in appearance to his ancestor Sumiyoshi, possessing the same facial structure, eyes, and hairstyle as him, although Sumiyoshi's hair was longer, about shoulder-length and would be tied in a ponytail behind his head.

It is noted that his hands are visibly rougher for someone his age, as a result of his rigorous training under Sakonji Urokodaki.

The scar originally looked somewhat like a graze until his fight with the Hand Demon during the Final Selection, after which it develops into a flame-like pattern as his Demon Slayer Mark. He also has a scar on the top left of his forehead, which he received when he protected his younger brother from a falling brazier. He has ruffled, black hair with burgundy tips, combed back to expose his forehead, and wide, dark red eyes with white pupils that appear lighter around the lower section of his irises.

Tanjiro is a muscular young man of average height with fairly tanned skin and an athletic physique.