Simon is a 17-year-old junior at Creekwood High School who has not yet disclosed that he is gay. He wears glasses, has gray eyes, and frequently listens to Elliott Smith. He comes from a progressive, loving family but struggles with the idea of having to reintroduce himself to everyone. He is emotionally driven, highly observant of his peers, and heavily involved in the school's theater community. He manages a complicated social life while corresponding with an anonymous classmate online.

Bram is a quiet, observant Black student at Creekwood High School who plays on the soccer team. He sits at Simon's lunch table and takes the same English class. Though he rarely speaks up in large groups, he is highly intelligent and carefully considers his actions before taking them. He often blushes when directly addressed.

Abby is a charismatic, extroverted junior who recently moved to the area from Washington, D.C. She is an active dancer and cheerleader, participating in the school musical and quickly becoming popular. Her long commute from College Park to Creekwood highlights the area's segregation. She is highly compassionate and stands up for her friends.

Leah is Simon's sarcastic, cynical best friend who has known him since sixth grade. She uses deadpan humor and subversive fashion to express herself. Deeply protective of her established friend group traditions, she often struggles when new dynamics or people are introduced into their circle.

Martin is a junior at Creekwood High School and a member of the school musical cast. Awkward and sometimes endearing, he struggles to make friends naturally. Despite considering himself a good guy, he acts selfishly and manipulatively to try and secure a date with Abby, causing significant distress to Simon in the process.

Nick is a long-time best friend of Simon and Leah. He is an easygoing soccer player who enjoys playing the guitar and hanging out in his basement. Nick serves as a central anchor for his friend group, though his shifting romantic interests sometimes cause unspoken tension among his peers.

Cal is the stage manager for the school musical. He is observant, artistic, and open about his bisexuality. He occasionally interacts with Simon during rehearsals and social events, prompting Simon to wonder about his personal life.

Nora is Simon's younger sister. She shares a comfortable home life with him and is highly observant of the social dynamics around her. She pursues her own interests quietly, including learning to play the guitar and playing in a band.

Alice is Simon's older sister who is currently away at college. Her absence leaves a noticeable gap in the family dynamic, especially during the holidays. She is managing her own transition into adulthood and a new relationship away from her parents' watchful eyes.

Simon's father is a politically progressive, attentive parent who tries to stay highly involved in his children's lives. He occasionally makes careless, well-intentioned jokes that unintentionally cause friction in the household.

Simon's mother is a caring but extremely nosy parent. She tends to make a major event out of any small change in her children's lives, from their coffee-drinking habits to their romantic interests, which often makes them self-conscious.

Ms. Albright is the drama teacher at Creekwood High School. She is fiercely protective of her theater students and maintains a zero-tolerance policy for bullying or harassment within her community.

Garrett is a student at Creekwood High School and a member of the soccer team. He is part of the athletic social circle and hosts social events that bring different student groups together.

Taylor is a perfectionist actress in the school musical. She takes her roles very seriously and is quick to defend her fellow cast members when they are threatened by outside bullies.

Peter is an attractive college student hanging out at a bar in intown Atlanta. He is friendly and conversational but maintains firm boundaries when he learns someone's true age.

Carter is Martin's older brother who is currently in college. He recently came out as gay, sending ripples through his family's dynamic and influencing Martin's perspective on sexuality.

Theo is Alice's college boyfriend. Because Alice's family is very nosy and prone to asking too many questions, she hesitates to introduce him to them too quickly.

Bieber is Simon's pet dog. He accompanies Simon on walks and provides silent comfort when Simon feels stressed or anxious about his social life.

Morgan is a student at Creekwood High School who shares a birthday with Bram. They celebrate with cake at the lunch table with the rest of the friend group.