Brother

Brother serves as both the main character and the narrator of the story. Although his real name is not mentioned, Doodle, his younger brother, calls him "Brother." When Doodle is born, Brother is six years old. Brother prides himself on his abilities to run, jump, and climb, and longs for a sibling to share these activities with. However, when it becomes evident that Doodle can do little more than lie on a rubber sheet and crawl backward, Brother feels ashamed of Doodle's limitations and often mocks him. Despite his love for Doodle, Brother's affection is marred by cruelty and embarrassment.

Encouraged by Doodle and their parents, Brother reluctantly allows Doodle to join him on his adventures, pulling him along in a go-cart. Motivated by the shame of having a disabled sibling, Brother devises a plan to secretly teach Doodle to walk. Eventually, he succeeds. However, this accomplishment does not satisfy Brother, who is determined that Doodle should not be perceived as different when he starts school. Brother pushes Doodle to engage in increasingly strenuous activities until one day, he runs ahead, leaving Doodle behind. Doodle overexerts himself trying to keep up and dies from a heart attack. Brother weeps over Doodle's body, realizing the symbolic connection between Doodle and the rare scarlet ibis that had fallen dead from a tree in their garden earlier that day.

Daddy

Daddy is the father of Brother's family. Shortly after Doodle's birth, he has a coffin made, believing Doodle will die. When Doodle survives, Daddy constructs a go-cart so Brother can pull Doodle around.

Doodle

Doodle, the narrator's younger brother, is both mentally and physically challenged. Initially, his family calls him by his given name, William Armstrong, but Brother nicknames him Doodle (after a doodle-bug, due to his tendency to crawl backward), and the name sticks. From the start, Doodle is a disappointment to his family, especially Brother, because he can only lie on a rubber sheet and crawl backward. Although everyone expects Doodle to die, he defies the odds and survives, becoming a loving child with a strong bond to Brother. Brother pulls Doodle around in a go-cart until he teaches him to walk. Nonetheless, this achievement appears to hold more significance for Brother than for Doodle.

Doodle's true strengths are not in his physical abilities but in his inner qualities, which Brother fails to recognize during the events. From the start, Doodle defies death and refuses to acknowledge the coffin Daddy builds for him as his own. He exhibits a profound sense of awe and respect for nature, marveling at the beauty of Old Woman Swamp. He is the first to notice the visiting ibis and carefully buries it, adhering to his mother's instructions not to touch it. Doodle's compassionate nature is highlighted by his decision to bury the scarlet ibis, establishing a symbolic connection between him and the bird. This connection is further emphasized when Doodle dies on the same day as the ibis, in a manner that mirrors the bird's fate.

Doodle's deepest fear is being abandoned by his impatient Brother during their outings. This fear becomes reality one day, leading to his death from a heart attack as he struggles to keep up with Brother.

Mama

Mama, the mother in Brother's family, has little hope for Doodle's future from the start. She tearfully predicts that Doodle will never be able to run or climb with Brother and fears he may not be mentally normal. When the scarlet ibis falls dead from the tree, Mama forbids Doodle from touching the bird, worried it might be diseased. Her attitude towards Doodle mirrors her reaction to the bird: in both instances, she only expresses fear and anxiety, failing to see the beauty and miracle.

Aunt Nicey

Aunt Nicey, the aunt of Brother and Doodle, is the one who delivers Doodle and the only person who believes he will survive. She has a religious disposition, offering thanks to God when Doodle demonstrates he can walk. Since Doodle is born with a caul, traditionally considered "Jesus' nightgown," Aunt Nicey insists he should be treated with special respect, suggesting he might become a saint. Although her belief is rooted in superstition, it reflects an appreciation of Doodle's spiritual qualities and hints at a symbolic link between Doodle, the ibis, and Christ.