Tōshirō is short, with turquoise eyes and short, spiked, white hair, which tends to draw attention in the Human World. He wears a standard sleeveless captain's haori with a green sash around his shoulders, held together by a round, star-like clip. The sash holds his Zanpakutō's sheath in place on his back and is tied to it at either end. He sometimes walks around in his tabi. He is relatively young by Shinigami standards, and has the appearance of a child. In the Human World, he wears a black, short-sleeved, golf shirt and gray pants. He also wore the uniform of Karakura High School.
Before Tōshirō was a captain, his hair was not as spiky, with only a few spikes here and there. He also wore the standard Shinigami outfit, but with the addition of the 10th Division's insignia on the left breast of his outfit.
17 months following Aizen's defeat, shortly after Ichigo regains his Shinigami powers, Tōshirō appears sporting a hairstyle similar to that before he became a Shinigami, and a long turquoise scarf. His green sash has also changed to a thin chain, but still retains the star-like clip.
After training for an unspecified amount of time in preparation to fight the Wandenreich, Tōshirō's hair appears to have grown longer, his fringe now reaching down to his eyes despite being held up by a newly acquired bandanna. He also appears lankier than before, with his robes loosely hanging off of his body.
After being zombified by Giselle Gewelle, Hitsugaya's appearance changes dramatically. He now wears a white double-breasted trench coat with black lapels that is fastened by four buttons on either side and which has a badge with a six-pointed cross on its left breast. He has a black belt with a large buckle around his waist, slightly baggy white pants, and white boots with furry black liners. He retains the thin chain holding his Zanpakutō's sheath around his upper torso.
Hitsugaya is generally mature and serious, in contrast to his free-spirited lieutenant, Rangiku Matsumoto. Despite their personality differences, he and Rangiku seem very close. Tōshirō is shown to be easily annoyed by others goofing off or drawing unneeded attention to themselves, as shown when he leads a team of Shinigami into Ichigo Kurosaki's school. Hitsugaya hates anything that he deems childish as well as being described as something close to a child, such as an elementary school child. He is overly protective of Momo Hinamori, due to the fact that they were old childhood friends. Hitsugaya dislikes summer and warm weather in general.
Tōshirō's favorite foods are watermelon and amanattō. He does not like dried persimmons. During his childhood in West Rukongai, he was so skilled with spinning tops that he became the local undefeated champion. He works very hard, but his motive seems to be that if he finishes quickly, he can return to his afternoon nap. He believes in the saying "children who sleep well, grow well," and hopes to grow quickly, a wish shared by his subordinates. Naturally, they do not voice this fact in front of him, for even regularly practicing this adage for so long, he did not really grow in height.
Hitsugaya is usually joked about by many of the other Shinigami in Soul Society as well as by his enemies. Hitsugaya has developed a cold attitude toward most people; he tolerates these jokes and goes on with his duties. Although he has shown anger towards jokes, he doesn't take action against whomever insulted him unless they are his enemies. The only thing he cannot tolerate is not being addressed as "Captain Hitsugaya," or an inappropriate use of his name, as he worked very hard for the title, so he gets angry when not addressed as such. He does not address any other officer with their title, only their last names. The only person that actually calls him by his given name is Ichigo, who is constantly reminded to address him properly, and Hinamori, who is the only person allowed to get away with it. Hinamori tends to call him "Hitsugaya-kun" and both she and Ukitake occasionally use "Shirō-chan" (シロちゃん) — a nickname meaning "Whitey" (Snowy in the English manga) in reference to his hair — in both cases without any repercussion. In addition, Karin and her friends call him by his first name and they are never given any rebukes for it. Jūshirō Ukitake often gives Hitsugaya candy and other food because "Jūshirō" and "Tōshirō" sound similar and because they both have white hair, making them both "Shirō-chan."
During his duel with Gin Ichimaru, Ichimaru remarks that Hitsugaya is the embodiment of a heavenly guardian that would be reincarnated every few centuries.