Bridge to Terabithia has three groups of characters: the Burkes, the Aarons family, and the significant teachers and students of Lark Creek Elementary School.

Jess Aarons, the most important character in the story and the one who determines the location of action, is the middle child between four girls. Two, Brenda and Ellie, are selfish adolescents used to getting around their mother. The other two, Joyce Ann and May Belle, are younger and look up to him. Jess is the victim of his older sisters and the protector of the younger, particularly May Belle. Mrs. Aarons seems worn out from children, work, and poverty, and she makes the mistake, as her husband does also, of separating chores into men's work and women's work. Jess, outnumbered, performs most of the chores around the farm, especially in the absence of his father. Jess would like a closer relationship to his father, but overwork and worries about money exhaust Mr. Aarons. Only when Jess is in desperate need, after the death of Leslie, do his parents show the care that they have not given him because of their fatigue and carelessness. Mr. Aarons is especially effective in finding the gestures and words that comfort Jess's overwhelming grief over Leslie.

Leslie Burke's parents are very intelligent but not always as responsible as they should be. Moving to the country to absorb by osmosis the rural virtues of simple living, Judy and Bill remain absorbed in their writing. Only when Bill finishes his co-authored book on politics and begins to fix up the old farmhouse does the relationship between him and his daughter flower. Leslie is hungry for the talk and the shared work; she appears to need from her father what Jess needs from his. The books and music, the awareness of a larger world that Jess, who helps in the work on the house, shares with the Burkes, delight him. The Burkes satisfy hungers Jess did not know he had.

Lark Creek Elementary School, poor and overcrowded, is the scene of much testing, outside as much as inside the classroom. It is the home of two teachers important to the novel, Miss Edmunds, who is young, sympathetic, and conscientious, and Mrs. Myers, who is old, overweight, and fearsome. Inwardly Mrs. Myers is caring, concerned, and much appreciative of Leslie's intelligence and talent, and later, sympathetic to Jess's grief. The two students most involved in the action are Gary Fulcher and Janice Avery. Gary, like Jess, wants to be the "fastest kid in the fifth grade" and is upset when Jess forces him into racing Leslie and being defeated by a girl. More important than Gary is the overweight bully, seventh-grader Janice Avery, who is the dragon Jess and Leslie imaginatively defeat when Janice steals May Belle's treasured Twinkies. The dragon, however, winds up being also a suffering girl who betrays the father that has abused her and is comforted by her former enemies and conquerors, Jess and Leslie.

The bridge building that one sees Leslie and Jess doing with their former enemy, Janice Avery, is representative of an activity one sees repeated many times in the novel. Miss Edmunds sees Jess's need, questions him about his drawing, and encourages him. Jess responds to her emotional gift with a smile and nods to the then lonely Leslie, and together they later respond to Janice Avery's pain. Jess's parents, at first unresponsive, emotionally locate their son, recognize his differences and needs, and give him the love he requires following Leslie's death. Their gift enables Jess to overcome his fear of drowning and rescue May Belle. Not content with a mere physical rescue, Jess, after formally mourning Leslie's loss in a ceremony of his own making, builds a bridge and welcomes May Belle, the new Queen of Terabithia, helping his sister to value her life as Leslie has helped him value his.

The theme of the novel thus seems to be a psychological response to the golden rule. Katherine Paterson's own religious values shape her story. Even the blows and curses are part of a longer chain of frustrated love, whether they be Janice Avery's or Jess's. For example, when Jess socks May Belle, he is angry, hurt, and lonely at his loss of Leslie. May Belle, hurt but wise in loving, ultimately responds to Jess's need, ignoring the blow, and loving her brother. For Paterson tragedy is a smaller event in a longer Christian quest.