Hiccup is the 10-year-old son of Chief Stoick the Vast and heir to the Hairy Hooligan Tribe. Physically small and more bookish than his peers, he is a self-proclaimed dragon nerd who studies dragons and speaks their language, Dragonese. The other boys mock his small stature and lack of traditional Viking aggression. He relies on his intelligence and research to solve problems rather than physical violence.

Toothless is a tiny, green Common or Garden Dragon caught by Hiccup during the novice initiation. Lacking teeth and physically unimposing, he mirrors Hiccup's underdog status within Viking society. He is stubborn, easily angered, and initially motivated only by self-interest, food, and silly jokes.

The Green Death is an ancient, gargantuan Sea Dragon larger than four blue whales. He possesses godlike power, vast intellect, and a philosophical worldview. He views all living creatures purely as food and threatens the existence of the Vikings on the island of Berk.

Stoick the Vast is the chief of the Hairy Hooligan Tribe and Hiccup's father. He embodies traditional Viking ideals of physical strength, loud charisma, and stoicism. He struggles to understand his bookish, undersized son but remains fiercely protective of his tribe and family.

Fishlegs is an orphaned boy and Hiccup's closest friend. Like Hiccup, he is considered useless by the more aggressive boys in the tribe. He is clumsy and easily frightened, but he remains a loyal companion throughout their dangerous trials.

Snotface Snotlout is Hiccup's cousin and primary teenage rival. He is a stereotypical Viking bully who prizes physical strength and aggression. Confident and ambitious, he desires to usurp Hiccup's position as the future chief of the Hairy Hooligan Tribe.

Old Wrinkly is Hiccup's maternal grandfather and the thinker of the Hairy Hooligan Tribe. He practices soothsaying and provides a rare voice of intellectual wisdom in a culture dominated by brute strength. He believes that Hiccup's unique qualities are exactly what the tribe needs for its future.

Gobber the Belch is the loud, physically imposing instructor in charge of the Dragon Initiation Program. He strictly enforces Viking traditions and rules, placing a heavy emphasis on courage, size, and the severe consequences of failure.

Thuggory is the son of Chief Mogadon the Meathead and the heir to the rival Meathead Tribe. Though he comes from a fiercely competitive clan, he demonstrates an ability to recognize true leadership when faced with a massive crisis.

Chief Mogadon leads the Merciless Meatheads, the primary rival tribe to the Hairy Hooligans. He is highly competitive and quick to insult Stoick's son, upholding the same physical, strength-based values as the rest of the Viking adults.

Dogsbreath is a large, brutish novice boy in the Hairy Hooligan Tribe. He acts as a loyal toady and enforcer for Snotface Snotlout, using his physical size to help bully the smaller boys like Hiccup and Fishlegs.

The Purple Death is a gargantuan Sea Dragon that washes ashore alongside the Green Death. It is even larger and more menacing than its green counterpart, presenting a secondary, massive threat to the Viking tribes.

Fireworm is a fearsome Monstrous Nightmare dragon belonging to Snotface Snotlout. Like her master, she is aggressive, boastful, and quick to pick fights with smaller, weaker dragons like Toothless.