Tadashi's younger brother. Since their parents passed away early, he lives at Aunt Cass's donut shop and calls his aunt 'Aunt Cass.' He is a brilliant robotics prodigy.

Hiro's older brother and the inventor of Baymax. He lives at Aunt Cass's donut shop and cares deeply for his brother and his colleagues. He is kind-hearted and hardworking.

A personal healthcare companion robot created by Tadashi Hamada. He is designed to help people and is incredibly soft and huggable.

The aunt of Tadashi and Hiro who took them in after their parents died. She runs a cafe/donut shop and also looks after their pet cat, Mochi. She is very affectionate and energetic.

Aunt Cass's pet Japanese Bobtail cat, often referred to as a 'hairy baby' by Baymax.

Tadashi's university classmate. She is tough, athletic, and always seen chewing gum. She develops high-speed electromagnetic wheel discs for transportation.

Tadashi's university classmate. She is a chemistry whiz who is always bright, optimistic, and cares for everyone around her.

Tadashi's university classmate. He is a perfectionist who needs his tools organized exactly in line and freaks out if things are out of place. He is cautious but loyal.

A major comic book fan who hangs out at the university. He often wears a mascot suit to promote the school and is the son of a wealthy family, though he acts very casual.