12-year-old Willow Chance is the novel's protagonist and the only character who provides a first-person perspective. She is the adopted child of Roberta and Jimmy Chance. Her name is doubly significant: she is named after a tree, symbolizing the growth and change she experiences throughout the novel, and her last name, Chance, invokes the fateful events that bind the rest of the characters to her. According to an evaluation done in kindergarten, she is “highly gifted,” though she thinks “it's not really a great idea to see people as one thing” (18). She considers herself “different,” “as in strange,” (9), and has never had an easy time making friends. Instead, she spends her time studying medical conditions and tending to her garden, which she considers her “sanctuary.” She “[doesn't] fit into an easily identifiable ethnic category” (11), has unruly, long curly hair and round “Gandhi” glasses. She looks nothing like her adoptive parents, but they nevertheless feel like a family.

When both of her parents die in a car accident, Willow suddenly finds herself without any family and questioning her purpose to live. The incident causes a shift in her character. The “new” Willow loses all interest in her old passions, but as she adjusts to her new life with the Nguyens, her interests slowly start to return.