Dragons are still dragons, and as a result, they are causing mayhem in the Isle of Berk. Stoick is reconsidering allowing the dragons to roam freely on Berk. It is up to Hiccup and his friends to convince Stoick otherwise.
The peace with the dragons has put Gobber out of business, since his job was making weapons to fight dragons. Stoick asks Hiccup to help find a new job for him ... but unfortunately a change of profession does not seem to go well with Gobber.
The dragons unintentionally reduce Berk's food productivity by still scaring the living daylights out of the local livestock, and with the first winter storm coming, the dragon-riding Viking youths of Berk must try and familiarize the local animals with their Dragon companions.
Hiccup finds an injured baby dragon. Toothless does not warm up to the energetic newcomer and the baby's angry mother arrives looking for her lost son.
The Dragons are blamed for vandalism, and Hiccup tries to prove their innocence by forming a night patrol called the "Dragon United Monitoring Brigade" (DUMB), but not in time to prevent the dragons' banishment from the island. Hiccup begins to suspect that Mildew is responsible for the scapegoat.
Hiccup had discovered Mildew framed the dragons but has destroyed all evidence of it, therefore he must prove of their innocence in order to get them back. Meanwhile, Alvin the Treacherous of the Outcast Tribe are on the mission to raid the Isle of Berk in order to find and capture the "Dragon Conqueror".
Stoick is in need of learning how to ride a dragon, and he quickly insists on riding Toothless all the time. Meanwhile, a mysterious dragon has been attacking fishing ships.
After getting his picture painted with his father, Hiccup begins to fear that he is not Stoick's ideal son, so to prove himself, he and his friends set out on a treasure hunt that even Stoick had not been able to complete.
After Mildew poisons all the dragons on the island, he is forced to help Hiccup, Stoick, and Gobber find and capture the ferocious Scauldron in order to get the antidote.
The teens of Berk find a mysterious girl named Heather on Thor's Beach. While Hiccup and the other teens openly welcome the newcomer, Astrid's jealousy turns to suspicion when she notices Heather is taking an unusual interest in the Book of Dragons.
Heather's betrayal to Berk caused the Book of Dragons to fall into Alvin the Treacherous' hands, and Heather's imprisonment on Berk. In order to get the book back from Alvin, Astrid disguises herself as Heather and goes into Outcast Territory. Towards the end of her mission, Astrid learns and confirms Heather's true motives for helping the Outcasts.
Berk's annual festive sporting competition, the Thawfest games, is underway and all the teens are participating with the dragons for the first time in Viking history. Hiccup is determined to finally best Snotlout, who constantly gloats about being the reigning Thawfest champion, but Hiccup's successes begin to make him arrogant and boastful, much to Astrid's displeasure and disappointment.
Sudden lightning storms are endangering the residents of Berk and it is believed Thor is angry at the island. Mildew leads the superstitious villagers into blaming Toothless, "the unholy offspring of lightning and death itself", for the lightning, leaving Hiccup to find the true answers for Thor's sudden destructive anger.
A rogue dragon: a Whispering Death, shows up in Berk, tearing up the village. He's on a mission to find Toothless and settle a score. Despite Hiccup's efforts to help, Toothless insists on facing the dragon alone. But unlike their past battle, Toothless's inability to fly may prove to be his undoing.
Dagur the Deranged visits Berk to renew a peace treaty between the Berserkers and Berk, and the dragons are put into hiding to dispel rumours that Berk is training a dragon army. But when Ruffnut and Tuffnut begin to fight, their dragon, Barf and Belch, is left out of control. The Viking youths must bring the twins back together to control their dragon and avoid provoking Dagur to war.
Caught in a waterspout, Toothless' prosthetic tail is damaged, rendering him unable to fly and thus leaving him, Hiccup and Snotlout stranded on Outcast Island. The three must work together to repair the damage, overcome the rivalry between Hiccup and Snotlout and return home to Berk before they are captured by Alvin and the Outcasts.
When Hiccup discovers Trader Johann's ship was shipwrecked in a rumored haunted bog with a gift made for him by his mother, he will stop at nothing to retrieve it.
When Snotlout and the villagers mistake dragon eggs for gems that bring good fortune, Fishlegs, who is responsible for the eggs' discovery, must take a stand against Snotlout and reunite the eggs with their Changewing mothers before they destroy Berk.
During Berk's annual Bork week celebrations, Hiccup is granted access to Bork the Bold's private and personal archives. When he finds information and a map about an island inhabited by Night Furies within Bork's notes, Hiccup is determined to bring Toothless to his family.
Mildew has betrayed the Vikings of Berk and allowed Alvin the Treacherous to kidnap Hiccup and Toothless. Stoick and Hiccup's crew must rescue them before it's too late.
Certain that Alvin is planning an attack on Berk, Stoick institutes flight restrictions on the dragon academy. Hiccup, certain that Alvin will be using his newfound dragon-training knowledge to bolster his attack, forms a secret “Dragon Flight Club” in order to train the kids to defend Berk against Alvin’s dragon army.
When Meatlug accidentally ingests magnetic rocks, she becomes magnetic herself - causing destruction through the town, but ultimately helping the kids win a battle against the Outcasts.
The kids go on a dragon survival-training mission to Dragon Island, where they encounter Dagur, the Berserker Chief, who has become obsessed with hunting the Night Fury.
Hiccup discovers that the town's water shortage has been caused by the Outcasts' plan to hide Whispering Death eggs under Berk, which soon hatch and tunnel under the island, threatening the villagers.
Hookfang is losing his ability to catch on fire, and it's up to Snotlout, Hiccup and the others to find the lair of the Fireworm Queen, which may hold the only possible cure, before it's too late.
Hiccup must help Astrid face her fear of the terrifying Flightmare, a ghostly dragon that seemingly "froze" her uncle with fear, shaming her family name. With Fishlegs' help, they discover that there's more to the Flightmare than meets the eye
A Terrible Terror training competition leads to a heated rivalry between Fishlegs and Snotlout, allowing Alvin to kidnap Meatlug. The kids must use their newly trained Terrors to rescue their friend.
When wild dragons start overwhelming Berk, Hiccup and Toothless discover islands are disappearing throughout the archipelago. When Hiccup and Toothless investigate the cause, they then encounter the Screaming Death.
While searching for traps, Tuffnut, Barf and Belch get trapped themselves... and a forest fire is approaching.
When the dragon riders discover a frozen Skrill, a lightning-powered dragon revered by the Berserkers, they scramble to get it off Berk.
Tuffnut goes undercover to help the riders rescue a Skrill.
Snotlout becomes convinced he is dying, and leaves Hookfang to Gustav. But when he "miraculously" recovers, Snotlout takes his dragon back, and Gustav decides to get a dragon of his own and join the academy... whether they want him or not.
Hiccup and co. discover an injured Scauldron on the shores of Changewing Island. The kids must heal the dragon and return him safely to the ocean, before he falls victim to the elements, as well as the territorial Changewings.
Hiccup and Toothless return from a mission to find Berk mysteriously empty. They discover that the village has been overrun by Speed Stingers, a venomous non-flying dragon that has trekked across the frozen sea to Berk.
Hookfang and Stormfly quarrel while the town prepares for the harvest.
Berk has been plagued with a bad case of the Eel Pox. Hiccup, Toothless and the gang, along with Gothi, go gather the ingredients for the cure. There's just one problem; the final ingredient is an eel from Eel Island.
The mysterious theft of metal objects all over Berk reveals the presence of marauding Smokebreaths. Hiccup and Toothless soon discover that these dragons are the work of Dagur, in a plot to render Berk defenseless.
When three adolescent Thunderdrums attack the village, only Stoick's Thornado can bring chaos to order.
Snotlout is expelled from the academy; Alvin returns to Berk to make amends.
Alvin reveals he trained the Screaming Death to attack Berk and destroy the island's inhabitants and only Snotlout and Hookfang can save Berk before it's too late. Meanwhile Hiccup gets ready for a final fight against Dagur to save Toothless and end the barbarians invasion of Berk once and for all.
During their search for the escaped Dagur the Deranged, Hiccup and the Dragon Riders discover a mysterious object -- one that holds their destiny.
Hiccup and the Dragon Riders journey to Glacier Island to find the Snow Wraith, a fearsome dragon that holds the key to the Dragon Eye's mysteries.
The Dragon Riders discover a lush island that turns out to be the home of the Deathsong, a massive dragon that threatens to trap them forever.
On an island that will make the perfect outpost, the Dragon Riders discover that the indigenous residents are a mysterious new breed of dragon.
Thinking he's allergic to his dragon, Fishlegs gets hypnotized. He wakes up transformed into an invincible warrior known as Thor Bonecrusher.
When Dagur the Deranged captures Gustav, it's up to Hiccup and the Dragon Riders to get him back.
Fireworms invade Dragon's Edge, while Ruffnut and Tuffnut discover that they have an unexpected connection to the island.
As a Rumblehorn wreaks havoc on Dragon's Edge, Hiccup seeks the help of Stoick, who forms an unexpected bond with the rampaging beast.
Fishlegs and Meatlug liberate the Gronckles from a menacing dragon that has encroached on their ancestral home, Dark Deep.
The Dragon Riders are surprised to discover who is behind recent attacks on nearby ships -- and to learn exactly what the ships are.
Heather joins the Dragon Riders, but it's not an easy alliance, especially when Hiccup uncovers a shocking secret about her true identity.
Hiccup and the Dragon Riders rescue a wounded Speed Stinger and take it back to Dragon's Edge, unaware of the dangers that follow.
When Hookfang is drawn to a female Monstrous Nightmare, Snotlout tries to break them up before he loses his friend forever.
After an attack on Berk, Astrid trains a crew of backup Dragon Riders to battle back -- but no one can guess how soon the next strike will hit.
A new enemy named Ryker Grimborn captures Stormfly, sending Hiccup, Toothless and the team off to rescue her before it's too late.
As Hiccup and Snotlout race to rescue the others from the Dragon Hunters, they don't realize that someone close to them is working with the enemy.
After a strange creature bites Tuffnut, he believes he'll turn into a legendary Lycanwing dragon when the moon is full. Can his friends save him?
Snotlout and Astrid must deliver a special battle axe to a family wedding, but when an Armorwing dragon derails their plan they have to work together.
After Hiccup and Toothless heroically save Barf and Belch, the grateful Zippleback tries to repay its life debt by abandoning riders Ruff and Tuff.
Ryker is determined to create a key to the Dragon Eye, so he heads to Glacier Island to find the Snow Wraith that the Dragon Riders are protecting.
When Ruffnut is captured by Dragon Hunters, it's up to Astrid and Tuffnut to defend Dragon's Edge from the invading Dragon Hunter army.
Unaware of the war on Dragon's Edge, Hiccup, Snotlout and Johann discover an island full of dragons that have been wounded by the Dragon Hunters.
When a new dragon is found in Edge Cove, the Dragon Riders must help the Sea Shocker escape a group of hungry Scauldrons.
The Skrill returns with a grudge against Hiccup and Toothless, and the Dragon Riders must choose a new course of action to stop the vicious dragon.
Hiccup and Astrid race to stop the Dragon Hunters from tracking the Flightmare after Heather spills secrets from Viggo Grimborn.
After Heather and the Flightmare have been captured by Viggo and the Dragon Hunters, Hiccup must hatch a plan to outwit the dangerous new enemy.
