Friendships among children are at the heart of The Adventures of Tom Sawyer. Tom's family—comprising Aunt Polly, Mary, and Sid—often fails to understand him and does not engage in his imaginative escapades. In contrast, Tom's friends, especially Joe Harper and Huck Finn, admire him for his creativity and adventurous nature. The boys see each other as they wish to be seen, creating an exciting world full of intrigue and adventure. The novel places particular emphasis on the bond between Tom and Huck. Tom appreciates Huck's freedom from adult constraints and enjoys the daring reputation that comes with their friendship. Tom genuinely cares about Huck, worrying about his loneliness. When they return from their pirating adventure to attend their own funerals, Tom and Joe are greeted warmly by their families, while Huck stands alone, without anyone to welcome him. Tom tells Aunt Polly, "it ain't fair. Somebody's got to be glad to see Huck." Tom and Huck share a strong belief in superstitions and a passion for adventure, imagining themselves as pirates and robbers. Tom's loyalty to Huck is evident as he continually defies Aunt Polly's orders not to play with Huck and even tells the schoolmaster that he was late because he was with Huck, knowing he will face punishment. The boys often use dramatic gestures to demonstrate their loyalty. For example, after secretly witnessing Injun Joe murder Dr. Robinson in the cemetery, Tom writes an oath stating "they will keep mum about this and … wish they may drop down dead in their tracks if they ever tell and Rot," which they sign with their own blood.

Being a child of the community and assured of adult protection, Tom feels secure enough to testify against Injun Joe during Muff Potter's murder trial. However, he keeps Huck's knowledge of the event a secret because Huck fears Injun Joe's vengeance and lacks real protection. Huck and Tom's friendship surpasses the social expectations of St. Petersburg. They are friends because they genuinely appreciate each other for who they are, regardless of society's disapproval.