Byakuya has slate gray eyes and long black hair, which he keeps up in intricate white headpieces called kenseikan, which symbolize his nobility as the head of the Kuchiki Clan, wearing one on top of his head and another two on the right side. In addition to the standard captain uniform, he wears a white scarf, which is woven by the master weaver Tsujishirō Kuroemon III. The scarf is made from silver-white, windflower light silk (ginpaku kazahana no uzuginu) and is a family heirloom, having been handed down from generation to generation and given to each head of the Kuchiki Clan. The scarf alone is worth ten mansions in the Seireitei. He wears fingerless white tekkō which only cover the back of his hands.
17 months after Aizen's defeat, Byakuya wears hairpieces at the back of his head, but it is noted that these hairpieces are not kenseikan. He wears a variation of the captain haori, featuring a high collar with light gold edges and small, light gold tassels attached to the corners. The white scarf is no longer part of his attire.
As the 28th Head of the Kuchiki Clan, Byakuya acts in an aristocratic manner. He always seems serene and apathetic towards other people, even while actually deeply conflicted. He is notably calm, even in battle. He generally acts indifferent, bordering on arrogance, to most situations he is faced with, and rarely views his opponent as being worth his time. Byakuya is easily offended if his name is not used properly. As such, he views Ichigo Kurosaki with disdain for always referring to him improperly. When Byakuya talks with Ichigo, he calls him by his full name. Byakuya is very perceptive, fully aware of the limits of his abilities, and anything he states in comparison to an opponent is usually justified. When he was younger, he was quick to anger and very hot-headed, as noted by his grandfather.
Byakuya strongly believes in law and order. As a captain of the Gotei 13 and head of one of the great noble families, he works hard for a peaceful society. He feels that if someone in his position does not follow the rules as a good example, no one else will. He believes that to maintain the order, all law-breakers must be punished, even if it goes against his own wishes. Byakuya feels that "part of a captain's responsibilities is to make sure that the lieutenant's responsibilities are taken care of". In spite of his icy and regal manner, Byakuya cares for and protects those important to him. After the events of the Aizen incident, he admits law isn't perfect, and becomes more lenient towards his adoptive sister, Rukia.
Byakuya is popular among the female Shinigami of Soul Society, and was voted number one in the "captain we desire to release a photo book for" poll taken by the Shinigami Women's Association. He likes Japanese cherry blossoms, night-time walks, spicy food, and bananas, but does not like sweets. Byakuya excels in calligraphy.