Akko Kagari is a slightly pale-skinned girl of average height with long, straight chestnut-brown hair that reaches just below her shoulder blades. Her hair features blunt square side-bangs on the left and a small half-ponytail at the back. She has large crimson eyes. As a child, her hairstyle was similar but shorter and without the ponytail. Early concept art depicted her with teal eyes and slightly longer hair.

At Luna Nova Academy, Akko wears the standard uniform of a white long-sleeved shirt, navy vest, matching tie, and skirt, often accompanied by a cape. During practical classes, she wears a traditional witch outfit consisting of a navy hooded tunic, pointed hat, belt, stockings, and boots, completed with a red sash like Lotte and Sucy. Outside school, she favors casual outfits such as a white T-shirt and brown shorts, an orange turtleneck, or an orange hooded jacket with red boots.

Akko is a cheerful, optimistic, and impulsive girl with exaggerated expressions and boundless enthusiasm. Highly social and compassionate, she inspires others through her kindness and unwavering belief in magic. Deeply influenced by her idol Shiny Chariot, Akko holds an idealized view of witches that often clashes with reality and leads to reckless behavior. Despite her flaws, she is not selfish and learns from her mistakes, particularly when they affect her friends.

Throughout the series, Akko struggles with insecurity over her lack of magical skill, especially when compared to Diana. Over time, she grows by accepting that she must succeed through her own qualities rather than imitation. While she remains impulsive, she becomes more self-aware, patient, and determined, earning respect from both allies and rivals.

Akko initially has poor magical aptitude due to her non-magical background and lack of discipline, particularly in broom flight. However, her potential is evident through her ability to wield the Shiny Rod and steadily improve. In the anime continuity, her weakened magic is revealed to be the result of Dream Fuel Spirit draining her power, forcing her to work harder than her peers.

She can perform basic witch magic such as energy projection, levitation, transformation, and object repair, with more destructive effects when using the Shiny Rod. Her signature skill is Metamorphosis Magic, which allows her to transform into animals or disguise herself as others after extensive training.