He seems fascinated by crime and death. He listens to Police Band Radio to keep up with what's happening in Beacon Hills.

He is the only character in the beginning of the series, other than Derek, who knows that Scott is a werewolf. He is very concerned with the well-being of his friends and family, though he doesn't always have the best ideas to keep them safe. He helps keep Scott calm and controlled. He plays in the lacrosse team at his school along with Scott.

Throughout the series, Stiles supports Scott through his troubles and helps him balance his double-life. He is attracted to Lydia and is often the comic relief in the intense drama of the show's events. He finds out information regarding werewolves and other problems and gives Scott ideas of what to do when Scott is at a crossroads.

Stiles is shown to be sarcastic, funny and outspoken. He sometimes finds himself in unwanted danger but is supportive no matter what. He loves his father very much and often worries about his well-being, especially since his father is the sheriff.

His Coach/Economics Teacher Mr. Finstock says Stiles is very bright but has trouble concentrating on anything he does not find directly of interest. His quick mind often leads him to jump to conclusions before all the facts are known.

Stiles suffered panic attacks after his mother died. His relationship with his father has been strained since her death.

In Formality, he takes Lydia to the high school formal dance, where he tells her about his true feelings for her. He also points out he may be the only one who knows how smart she actually is, and not just a dumb bimbo. He saves her from being killed by Peter Hale by telling him how to find his nephew, Derek.

In Code Breaker Stiles is forced to help track Derek down. Peter offers to give him the "Bite", which is tempting to him, but he rejects. Peter knows he is lying, and then drives off. Stiles makes his way to the hospital and puts together that Kate Argent started the Hale House fire. Later, he and Jackson Whittemore are interrogated by the Hunters for the whereabouts of Scott. Stiles reveals to Chris that Kate broke the Hunter's code. Soon after that he and Jackson arrive at the Hale House with self-igniting Molotov cocktails to fight the Alpha. He helps defeat Peter and witnesses Derek become the new Alpha Werewolf.