Shoto originally had a cold, aloof personality which stemmed from his abusive upbringing. Focused and unemotional, Shoto preferred to keep to himself instead of hanging out with other people. After the events of the U.A. Sports Festival, however, Shoto has become noticeably more sociable, even gaining a sense of humor and occasionally smiling, although still retaining the remnants of a distant attitude. After the events in the Remedial Course Arc, he has began to open up more to his classmates and has lightened up from his usually serious demeanor.
Additionally, Izuku is a quite diligent and strong-willed student. His dream drove him to write down notes about everything he knows in regards to Hero's Quirks. Because of this practice, Izuku has developed a great analytical mind and can form complex battle plans in seconds, which factor in both his allies' and enemies’ Quirks. Izuku externalizes his observations through endless mumbling, a habit which annoys or scares his peers. Izuku often writes down his observations in a notebook he refers to as Hero Analysis for the Future.

Despite his usual reserved demeanor, Shoto did initially possess a moderate level of arrogance, which, combined with his solitary tendencies, sometimes made him take the initiative without considering the opinions of others, as he was confident that he could take on any obstacles with his own strength. He used to be much more unfriendly as well, to the point of causing someone to resent him.

Shoto is quite seasoned in battle, being able to stay calm and composed even while fighting real villains. Though brutal in combat, Shoto is well-grounded on the ethics of heroism, only wishing to subdue his frozen opponents as opposed to killing them by prolonging their frozen states. Shoto appears to draw his heroic values from All Might, which is a trait he shares in common with Izuku Midoriya and Katsuki Bakugo.

Shoto had a deep loathing for his fire abilities, which he inherited from Endeavor, as it symbolized his father's wickedness towards him and his mother as well as what he was born to be: a tool to surpass All Might, a fate that he detests. As such, Shoto decided to rely solely on his ice power and never use the other half of his Quirk in battles, going so far as to cover his left torso and arm with ice in his first Hero Costume to symbolize his rebellion against his father. His flames would be used only to undo his freezing moves.

During his match with Izuku in the U.A. Sports Festival, Izuku's speech made the memory of his mother's supportive words resurface, and for the first time since his childhood, Shoto used his fire power in combat. After the battle, Shoto had mixed feelings about using his left side, but after reconciling with his mother, Shoto eventually came to terms with the half he once hated. Despite being scarred by her when he was a young child, Shoto showcases no hard feelings towards his mother, visiting her often ever since the end of the Sports Festival.

However, Shoto still harbors a grudge towards Endeavor, even if he respects his father's ability as a Hero, admitting to himself that such resentment can't vanish so easily and that he was wrong in trying to bury it. Having been denied a normal childhood so that his father could train him to realize his own selfish ambitions, Shoto still holds various psychological scars, which tend to reemerge when others compare him to Endeavor. Because of this and Izuku's influence, Shoto now strives to become a Hero, but without walking the same path his father did.

Shoto still remains cold towards Endeavor and has made it clear that forgiveness for his past treatment of him and his mother is difficult, but has demonstrated to worry about his father's safety. With Endeavor now attempting to improve his relationship with his family, Shoto has taken a cautious, yet hopeful approach to this development.