Kenpachi is a tall, muscular Shinigami with a wild and aggressive appearance, which fits his personality. He has a long face with pronounced cheekbones, and pronounced, hairless eyebrow ridges. He has green eyes and long, stringy black hair. A noticeable trait in his appearance is a long, thin scar running down the left side of his face, inflicted on him by Retsu Unohana. He is one of the tallest Shinigami, towering at 202 centimeters (approximately 6 feet 6 inches), making him almost double the height of his lieutenant.
He wears a sleeveless captain's haori (which belonged to the previous captain and was taken after his defeat), which has a ragged look to it. He styles his hair into stiff strands during his baths, attaching small bells at its tips, and wears a special eyepatch on his right eye. During his first fight with Ichigo, the eyepatch is more elegant, having a gold-like lining and a chain as one of the straps. It later becomes a normal black eyepatch with normal straps.
17 months after Aizen's defeat, Kenpachi's hair has grown out past his shoulders. He no longer has the bells in his hair. His eyepatch's design has changed again, as it is now, but a single piece covering his right eye. The eyepatch is black with a grey outline.
Although he is known to be a violent fighter, Kenpachi's actions tend to be for the best. He has a very poor sense of direction, at times asking Yachiru for help (even though her sense of direction is just as bad). Kenpachi lives for battle, and enjoys a good fight more than anything. He even holds back in an effort to make any fight last longer. He claims injury and death are nothing but the price one pays for a good fight. Despite his division being the most blood-thirsty squad of the Gotei 13, the 11th Division has its own code of ethics, which is different from the rules and regulation of Soul Society. Despite his tendency to be brutal, Kenpachi usually stops a fight if his opponent is too injured to fight back, claiming he is not interested in fighting "weaklings who can't fight anymore", and he does not feel obligated to deal a death blow to anyone who cannot fight any longer. However, he will unhesitatingly kill his opponent if they refuse to end their fight, as seen during his battles with Kaname Tōsen and Nnoitra Gilga.
On multiple occasions, Kenpachi has shown to greatly respect those who can defeat him in a fight and those who can push him to his limit. Ever since Ichigo handed him his first known loss (though Ichigo considers their fight a loss for him), Kenpachi has considered the latter a member of his Division. He expresses his willingness to engage him in a rematch every time they meet, only to be turned down, as Ichigo already considers themselves as friends. Nevertheless, Kenpachi still challenges him to a duel, as evidenced when he aided Ichigo in his fight against the Bount (where he gave "his blessing," stating doing so would make Ichigo stronger for "their anticipated fight").
Kenpachi sometimes contradicts his own logic in fighting. On the one hand, Kenpachi wishes to increase his own personal power. On the other hand, he conceals his strength to enjoy a fight for as long as possible. Although he thrives for battle, Kenpachi does have emotions. Kenpachi and his lieutenant, Yachiru, have been close ever since they met, and have a father-daughter-like relationship, making Yachiru one of the few people he cares for, along with 11th Division 3rd Seat Ikkaku Madarame and 11th Division 5th Seat Yumichika Ayasegawa. However, he has stated if his subordinates interfere in his fights, he will "cut them up first". Aside from Yachiru, Kenpachi deeply gives meaning to his name. Following his fight with Ichigo Kurosaki, Kenpachi talks about the pain of not having a name, as he lived his early years without one. This causes him to feel guilty his sword is not acknowledged by its own name. Since then, he has strived to learn its identity.
Kenpachi strongly believes fun comes before working. In every battle, he tries to get as much enjoyment out of it as possible. One example is when Kenpachi sends his 5th seated officer, Yumichika, to fend off the Bount in Karakura Town, as he is the only high-ranking officer who is not busy, or rather, busy having fun, as Yachiru was snacking and Ikkaku was napping. During his free time, Kenpachi always takes his afternoon nap. He does not have a particularly favorite dish, but he particularly hates nattō.
Kenpachi's unique hairstyle is partly due to his habit of taking a bath everyday before going to sleep, which is a necessity to him due to his strong perspiration. During these baths, he usually washes his hair with soap, making it stiff. He enjoys doing so because it is easy for him to set his hair to his preferred style. He once tried a hair treatment recommended by 1st Division Lieutenant Chōjirō Sasakibe, but his hair became too silky and was impossible to set for a while. Since then, Kenpachi has greatly disliked the lieutenant. Kenpachi is once shown attaching the bells to his hair, which apparently takes a while to accomplish. The highest bell in particular takes him several hours to attach, as the tip of his hair is just beyond his reach. Occasionally, 11th Division 5th Seat Yumichika Ayasegawa offers to do it for him, only to be turned down by Kenpachi, who thinks it is weird for someone else to style his hair.