All Might's hero persona appears to be derived from western superhero stereotypes. His personality is very colorful and tends to have a lot of dramatic flair. Always sporting a giant smile, All Might usually show off a bright, borderline obnoxious, can-do attitude to inspire others. He tends to be extremely friendly and amicable, due to his popularity and years in the spotlight. However, when he reverts to his sick and scrawny form, he tends to be less energetic. He loses the need to hide his worries about the state of affairs around him behind his smile. Additionally, he avoids drawing attention to himself altogether, afraid that others might learn of his current state of health.

All Might has a fatherly attitude towards his students (Izuku in particular) and takes pride in helping better his students as heroes. He is quick to give encouraging advice to them and often says he is proud of their improvements. On several occasions, All Might has tried to help mend Katsuki's pride and his relationship with Izuku. All Might was not afraid of pushing Izuku and Katsuki during their final exams and pulled no punches because he knew he needed to do his best to teach them both a lesson. He even used a villainous persona during their battle to get his point across, which both Izuku and Katsuki described as very intimidating.[3] He also has a habit of adding "young" (少年 Shonen?) to the surname of his students whether he is speaking out loud or thinking to himself (ex. "Young Midoriya"). While All Might is seen smiling, laughing, and cheerful most of the time, he is extremely protective of his students and his rage will show if they're in danger. He was willing to use his Quirk beyond his time limit in order to save his students from the League of Villains. In spite of his anger, he made sure his students felt safe by showcasing his trademark smile before the fight.