A seventeen-year-old student at Bayview High, self-proclaimed “omniscient narrator,” and antagonist of the story. Simon is an outcast who terrorizes other students by exposing their darkest secrets. Simon suffers an allergic reaction while in detention and dies. Though he was largely hated in life, in death he earns the renown he’s always longed for.
A student at Bayview High and “the brains” of the Bayview Four. Bronwyn dreams of attending Yale, and she is a gifted pianist and general overachiever. Her family lives in a large Victorian house in the affluent part of town. As the daughter of a Columbian immigrant, Bronwyn is the book’s only multiracial character.
A student at Bayview High and “the criminal” of the Bayview Four. Nate earns a bad reputation for selling drugs and is on probation for selling marijuana and painkillers. Nate has been forced to grow up quickly due to his absent, drug-addicted mother and alcoholic father.
A seventeen-year-old student at Bayview High and “the jock” of the Bayview Four. Cooper is a star baseball player with a bright future. Originally from Mississippi, Cooper’s southern drawl emerges when he becomes nervous. Cooper is close with his tight-knit, conservative family and is well-liked by the Bayview community, but he feels pressured to hide the fact that he’s gay from almost everyone.
A seventeen-year-old student at Bayview High and “the princess” of the Bayview Four. Addy is popular and has been dating her athlete boyfriend, Jake, since their freshman year. Addy is often perceived as weak, needy, insecure, and superficial, though she ultimately proves that she is strong and independent.
A student at Bayview High and Addy’s boyfriend. Jake is popular and a member of the football team. He is generally well-liked but sometimes exhibits controlling tendences and frightening rage.
A student at Bayview High and the “goth” girl. Janae is Simon’s only friend.
The host of the Mikhail Powers Investigates news show. His reporting on Simon’s murder and the potential involvement of the Bayview Four suspects garners national attention for the case.
A student at Bayview High and Bronwyn’s younger sister. Maeve had leukemia from ages seven to fourteen and was unable to attend school and interact with her peers. She is smart and skilled with computers.
A student at Bayview High and Jake’s friend. TJ is kind to Addy and admires her personality.
Addy’s twenty-something older sister. Ashton returns home after her marriage dissolves and often serves as a maternal figure to Addy. She is protective of her younger sister and encourages her independence and development.
A pro-bono lawyer for Until Proven. He is a guest on Mikhail Powers Investigates and becomes a champion for the students’ rights. Eli eventually becomes Nate’s lawyer.
Addy’s self-absorbed and materialistic mother. She has been married several times and is dating a man half her age. Ms. Calloway believes women are only valuable if they are pretty enough to attract a successful man.
A science teacher at Bayview High. Mr. Avery abhors social media and technology. He criticizes his students for their reliance on technology and punishes them with detention when they bring cell phones into his classroom.
Cooper’s grandmother and the only adult in Cooper’s life who sees and accepts him for who he really is.
A student at Bayview High and Cooper’s loyal best friend.
Cooper’s girlfriend and Simon’s crush. Keely is popular, sweet, and beautiful, though she is not always a loyal friend.
Cooper’s secret boyfriend who helps solve the mystery of Simon’s death.
Nate’s probation officer. Officer Lopez is sympathetic to Nate’s troubled home life and occasionally serves as a motherly figure to him. For some time, she is the sole adult figure concerned about Nate’s well-being.
A student at Bayview High who attempted suicide because of the gossip spread about her through Simon’s app.
A student at Bayview High who was outed on Simon’s app for cross-dressing.
A popular but cruel girl at Bayview High. She has a crush on Jake and bullies her former friend Addy.
A student at Bayview High. Kate is one of Bronwyn’s close friends.
A student at Bayview High. Yumiko is one of Bronwyn’s close friends.
Detective Wheeler, Detective Mendoza, and Detective Chang
The Bayview Police Department detectives assigned to work the case of Simon’s murder.
A policeman with the Bayview Police Department. Officer Budapest is the one of the first officers to question the Bayview Four.