Gene is the protagonist and narrator of the novel. He is an academically minded student who later discovers that he has some athletic talent as well. Gene's best friend is Finny, but Gene causes Finny to fall from a tree early in the novel, injuring Finny's leg severely.
The competition and complex relationship between Gene and Finny animates much of the novel.
Finny (a.k.a. Phineas) is a free-spirited and rather innocent person with a natural athletic ability that allows him to break school records with relative ease. He plans to compete in the Olympics and this plan seems actually achievable for him until his injury. Finny is charming and captivating. He remains cheerful after his injury, but becomes a confusion of sorts for Gene and for Brinker. Finny denies the existence of WWII, confusing Gene, and refuses to explore the exact causes of his accident, confusing Brinker.
Other characters in the text include Brinker (a natural leader with a compulsive need for clarity and action) and Leper (a socially awkward, scientifically minded boy who enlists early and then runs away from the army).