- The novel's protagonist. Dicey is a thirteen-year-old girl with a haircut that makes her look like a boy and a fierce determination to survive and keep her family together. Dicey, as the oldest child of a mentally unwell single mother, is used to playing the role of an adult in her family, but when their mother abandons them in a parking lot in Rhode Island, Dicey steps into greater responsibility than she ever had. Dicey is tough, pragmatic, and suspicious of anyone outside of the circle formed by her immediate family, only taking help from others when she absolutely needs to do so. She is willing to do everything within her power and take any risks necessary to protect her siblings and keep them together.
- Dicey's twelve-year-old brother. James is serious and intelligent, and unlike Dicey, cannot fight to defend himself when his peers tease him about his family. Consequently, James withdraws into his studies and philosophical musings. He reacts to Momma's departure more harshly and judgmentally than Dicey, and occasionally indulges in criticism of her lifestyle to help explain why she left them. He looks up to Dicey and relies on her to make decisions, but can also act rebelliously and selfishly.
- Dicey's eight-year-old sister. Maybeth is a quiet and pretty young girl troubled by an overwhelming shyness. Her shyness and difficulty performing in front of others have resulted in her being held back in school and in the perception of her peers and teachers that she is mentally retarded. The Tillermans know differently. Maybeth is uncannily emotionally perceptive and can quickly and easily sense the emotional truth behind people and the implications of the situations in which they find themselves. Maybeth takes after Momma physically, and can sing beautifully.
- Dicey's six-year-old brother. Sammy is a stubborn and uninhibited child. Momma's favorite, and as the youngest, he is perhaps hardest hit by Momma's disappearance. Like Dicey, Sammy has learned how to fight to ward off the taunts of his peers, which are even worse for him than for Dicey because the children tease him about Maybeth as well as about Momma. Thus, Sammy is belligerent, aggressive, and stubborn, but often, especially with his family, he is joyful, spontaneous, and utterly free. This recklessly happy side of Sammy is part of what wins Gram over in the end of the book.
- The Tillerman children's grandmother and Momma's mother. Gram lives by herself on a run-down farm outside of Crisfield, Maryland. Gram shares Sammy's belligerence and stubbornness and Dicey's determination. Gram has been hardened by a long marriage to a stern and unloving man, now four years dead, and her stubborn conviction to stand by him and his decisions, even when she disagreed with him. Her unhappy marriage has made her angry and bitter, and caused her to become estranged from all her three children.
in-depth analysis of Gram.
- The Tillerman's mother. Momma decided when she left home at the age of twenty never to marry, having learned from Gram's sad example. Momma is loving and beautiful, but is neither reliable nor practical. When Momma is pregnant with Sammy, their fourth child, the childrens' father leaves her, possibly under legal duress. Momma struggles under the responsibility of raising her four children on her own, but eventually buckles under the pressure.
- The Tillerman children's cousin. Eunice is Gram's sister's daughter. Eunice is a pious Catholic used to her routine and very nearly incapable of spontaneity and affection. She takes the Tillerman children in out of a sense of duty, but, consciously or not, expects the children to show gratitude and earn their keep through their good behavior and hard work. Fussy and flighty, Eunice lives a carefully scripted life.
- Eunice's priest. Father Joseph is a well-intentioned but ultimately unsympathetic man. Eunice relies on him for advice when the Tillerman children appear on his doorstep. Though, from his perspective, he has the good of the children firmly in mind, he never truly tries to understand them or reach out to them. Like Eunice, he is guided by a sense of piety, religious duty, and propriety.
- One of a pair of runaways the Tillerman children meet in a state park in Connecticut during the first half of their journey. Louis is selfish and immoral, rationalizing theft and irresponsibility as a way of rebelling against an unjust system.
- Louis's girlfriend. Edie buys into Louis's cynical and self-indulgent philosophies about life and right and wrong. Louis convinced her to steal money from her father and run away with him, and occasionally he teases her and treats her cruelly. Edie is a gentle girl and plays the autoharp, so the children warily agree to spending time with the couple.
- A garrulous and friendly Yale undergraduate who takes the Tillermans in one rainy night in New Haven. Windy explains his generosity by telling the children of his own experiences as a young runaway. Windy is non-judgmental, spontaneous, and fun.
- Windy's roommate. Stewart is quieter and more serious than Windy, but just as generous and open-hearted. He talks gravely to James about the personal implications of stealing, and plays the Dobro, teaching the children a song they take with them all the way to Crisfield. Stewart drives the children to Bridgeport in his car.
- One of the two boys who takes the Tillermans across the Chesapeake Bay on a sailboat. Tom is a little overweight and enjoys daring his friend, Jerry, to take risks.
- Tom's friend. Jerry is the true sailor of the pair and is more contemplative than Tom. Jerry is impressed by Dicey's sailing skill and flirts with her during their trip.
- The owner of the circus. Will saves the children from Rudyard and drives them to Crisfield. Will is a caring and philosophical man who enjoys the rootlessness life in the circus affords him.
- One of the workers in Will's circus. Claire has a nasty temper which at first intimidates the Tillermans but later rescues them from the dastardly Rudyard.
- A farmer in southern Maryland. The children meet Rudyard when they offer to work picking tomatoes for him. Mr. Rudyard, however, intends them harm.
- Gram's sister and Momma's aunt. Cilla writes cards to Momma every year. Momma drives to her house in Bridgeport, hoping she can help them.