Arnold, universally known as Junior on the Spokane Indian Reservation, is a bright teenager who views his difficult world through humorous drawings. He copes with physical challenges such as poor eyesight, a large skull, and a stutter, making him a frequent target for bullies in his community. Despite the intense poverty surrounding his family, he maintains a sharp intellect and a deep desire to build a better future. He makes the difficult choice to attend the predominantly white Reardan High School, creating a deep identity conflict as he splits his life between two vastly different worlds.

Rowdy is a tough, physically aggressive teenager who has grown up alongside Junior on the reservation. He expresses his emotions almost entirely through anger and physical violence, fighting regularly to assert dominance. At home, he suffers under an abusive, alcoholic father, leading him to treat Junior's house as a safe haven. He views Junior's decision to attend Reardan High School as an unforgivable betrayal.

Junior's father is a man with unfulfilled musical aspirations who struggles heavily with alcoholism. He sings the blues and keeps an old saxophone clean, representing his deferred dreams. Despite his addiction and poverty, he is an emotionally present parent who never resorts to physical violence, and he supports his son's effort to find a better education.

Gordy is the intellectual standout at Reardan High School. He operates with a highly analytical mindset, frequently quoting literature and explaining social dynamics through an academic lens. Though he occasionally lacks social grace, he teaches Junior how to find genuine joy in hard work and reading.

Mary is Junior's intelligent and eccentric older sister, often called "Mary Runs Away" by her family. After giving up her early dreams of writing romance novels, she isolates herself in the family's basement for years. She eventually displays a spontaneous streak, making abrupt choices to seek out a completely new life away from her parents.

Agnes is Junior's mother, a voracious reader who possesses a remarkable memory. Junior believes she could have been a successful college professor if she had been given the necessary resources. She is a former alcoholic who deeply loves her children and worries intensely about how the reservation community will react to Junior leaving the local school.

Grandmother Spirit is a highly respected elder on the Spokane reservation. She embodies the traditional Native American spirit of tolerance, openly embracing people's differences. Unlike many adults in Junior's life, she never consumes alcohol, preferring to remain fully alert and connected to the world around her.

Penelope is a popular, blonde student at Reardan High School. Underneath her socially accepted exterior, she deals with immense personal pressure and copes through bulimia. She harbors dreams of leaving her small town to study architecture at Stanford, finding common ground with Junior's own ambitions to escape his current circumstances.

Roger is a star athlete and an influential older student at Reardan High School. He initially clashes with Junior through severe bullying, provoking a physical confrontation. Over time, he demonstrates a surprising capacity for generosity, eventually helping Junior handle the social and financial challenges of attending the school.

Mr. P is an older, lonely white teacher working at the Wellpinit school. He carries deep guilt over his past participation in an educational system designed to eradicate Native American culture. Recognizing Junior's potential, he actively pushes the teenager to leave the reservation.

Eugene is Junior's father's best friend and a constant presence on the reservation. He rides a motorcycle, works toward becoming an Emergency Medical Technician, and serves as an encouraging figure for Junior. Like many adults on the reservation, he struggles with alcohol use.

The basketball coach at Reardan High School is a demanding but supportive leader. He recognizes Junior's shooting skills and commitment despite his small stature, placing him on the varsity squad as a freshman. He provides crucial emotional support during highly stressful moments.

Oscar is the Spirit family's pet dog and Junior's trusted companion. When he becomes violently sick, the family's extreme poverty prevents them from seeking veterinary care, illustrating the harsh economic realities of reservation life.

Rowdy's father is a heavy drinker who subjects his family to physical abuse. His violent behavior and use of homophobic slurs directly influence his son's aggressive personality and difficulty with emotional expression.

Earl is Penelope's father, a resident of the predominantly white town of Reardan. He holds overtly racist views and makes his hostility toward Junior clear, creating tension in Penelope's social life.

Mr. Dodge is a Reardan science teacher who dismisses Junior's knowledge about petrified wood. He openly mocks the educational standards of the reservation school until Gordy verifies Junior's correct scientific explanation.

Ted is a wealthy white collector of Native American artifacts who fetishizes Indigenous culture. He attends a reservation funeral hoping to return a powwow dance outfit, only to display his profound ignorance of specific tribal traditions.

The Andruss brothers are thirty-year-old triplets living on the reservation. They use their physical size and age to bully younger community members, eventually targeting Junior until they face severe retaliation.

Miss Warren is the guidance counselor at Reardan High School. She is tasked with the difficult job of locating Junior during the school day to deliver highly emotional family news, showing sympathy for his situation.

Mrs. Jeremy is a teacher at Reardan High School who shows a lack of empathy for Junior's personal struggles. When she criticizes his prolonged absence, she inadvertently sparks a classroom protest led by the students.