Unohana has the appearance of a slender and very youthful woman with blue eyes and black hair. She wears the standard Shinigami captain uniform apart from using an obi instead of the normal sash. Her hair is long and is always worn as a large braid down the front of her body. Over 100 years ago, she did not have the large braid, instead styling in front of her as a loose ponytail. While maintaining a kind and gentle look at most times, during her battle with Kenpachi Zaraki, her eyes appear gloomy and very menacing. She also wears her hair down for the first time and is revealed to have been covering a notable scar in-between her collarbone, inflicted by Kenpachi when the latter was young. Before Kenpachi inflicted that scar on her, she did not tie her hair in front of her, instead wearing it down at all times.
Unlike most Shinigami who carry their Zanpakutō in their sash, Unohana has a large string attached to the sheath of her Zanpakutō and carries it over her shoulder, or has her lieutenant, Isane Kotetsu, carry it for her whenever they are together on the battlefield.
Unohana has a gentle and warm personality that augments her appearance. Unohana is a soft-spoken, polite, and caring woman who uses honorifics when addressing everyone, including her subordinates and the enemy. She rarely shows any signs of panic or distress, and has a great sense of duty, shown in the times that she orders Hanatarō Yamada’s imprisonment and Isane Kotetsu’s chasing of Renji Abarai when he runs away with Rukia Kuchiki. Despite her sense of duty, she will also heal almost anybody around her, including Renji after he was defeated by his captain, Gantenbainne Mosqueda when she arrived in Hueco Mundo, and the Visored, referring to them as allies despite Shinji's reluctance to do so. With her grace and kind manners, she lets others know quietly that while she may be soft, she is not to be taken lightly. Despite her gentle nature, several members of the Eleventh Division and even her fellow Captains fear her.
However, after the revelation of her past as the first Kenpachi and Shunsui Kyōraku calling on her to draw on her experience from then, Unohana's personality reverts to her original violent and bloodthirsty nature; once she meets with Kenpachi Zaraki, she comments how the scar left on her chest was causing her pain just from the sound of his voice. Unohana herself says that she is infatuated with crossing blades, and firmly believes in taking any actions necessary — even sleight of hands such as hidden daggers to get ahead in battle.
Unohana likes strong-flavored food, preferring it to bland tasting dishes. In her free time, she climbs mountains throughout Rukongai; during these excursions, she collects medicinal herbs. Once a month, she holds an ikebana class for the members of her division and she is also the President of the Ikebana Club.