|“You will make the impossible possible, and unify the elemental powers of Fire and Water.”|
|— Maya to Kai and Nya in "Out of the Fire and Into the Boiling Sea"|
Notable Fusion Dragons
- Ultra Dragon (Fire, Earth, Ice, Lightning)
- Hydro-Electric Dragon (Water, Lightning)
- Fusion Dragon (Fire, Water)
Nya and Lloyd attempt to stop the Great Devourer by wedging a street light in its mouth using the Samurai X suit, only to get stuck when the suit malfunctions. Before they can be consumed, the Devourer is attacked by the Ninja's Dragons, now merged as the Ultra Dragon. After saving Nya and Lloyd, the Ultra Dragon swoops in to attack the snake, with the Ninja cheering it on. The assault seemingly forces the Great Devourer to retreat, but as the Ultra Dragon glides to its allies, the serpent's tail shoots out of the ground and knocks the Dragon out of the air.
When the Ninja moved into the Hero Suite, the Ultra Dragon stayed in the built-in dragon keep on the roof where it rested, still recovering from the injuries inflicted by the Devourer.
Nya gave Lloyd a short dragon lesson while she was feeding the Ultra Dragon his medicine, informing him that while the four elemental dragons belonged to the four Ninja, the Ultra Dragon belonged to him. Strengthened already, the Ultra Dragon then took off from its resting spot atop a building to go stretch its wings.
The Ultra Dragon flew over the Endless Ocean where he came upon the Black Bounty, manned by Lord Garmadon and the Serpentine. The dark ship pursued the Ultra Dragon over the ocean, but he escaped without injury due to Garmadon not realizing that his new Mega Weapon could only be used to create, not destroy.
The Ninja rode the Ultra Dragon to Darkley's Boarding School for Bad Boys when Lloyd received an invitation from his former classmates to a party in his honor. Brad Tudabone was suitably impressed when he saw Lloyd's new means of transport. After overturning the students' plot to turn Lloyd evil and fighting off the Bizarro Ninja, Cole rode the Ultra Dragon home while the other four Ninja rode in the Ultra Sonic Raider.
Lloyd enters the Ninjaball Run with the Ultra Dragon as his transport. He accidentally rammed The Black Bounty during the desert portion of the race, ruining Lord Garmadon's attempt to attack the Ninja. In the Glacier Barrens, Lloyd uses the Ultra Dragon to spot a shortcut for the Ninja's use, only to be knocked out of the race by Kruncha and Nuckal's Skull Truck (although it also caused the Skulkin vehicle to crash). The Ultra Dragon eventually recovered and returned to Ninjago City, where he helped Lloyd reclaim the Black Bounty from Lord Garmadon.
The Ultra Dragon escaped the Overlord's attack on Ninjago City and flew to the Island of Darkness, where he gave the Ninja, Master Wu, Misako, and Dr. Julien a ride back to Ninjago. He took part in the assault on the Overlord's fortress, being piloted by Master Wu when the Ninja jumped off to aid Lloyd in fighting the Stone Army, but was eventually taken out of the fight when Nya—corrupted by Dark Matter—hit him with a shot from a turret on the tower. The Ultra Dragon recovered in time to reunite with the Ninja after Lloyd defeated the Overlord.
The Hydro Electric Dragon was created in when Jay and Nya were the only Ninja who weren't trapped in the Sword of Souls. After falling off the Misfortune's Keep, they weren't able to summon their own dragons for their battle with the Sky Pirates had weakened them. They came closer, and started holding hands, forming a fusion ball of Water. The Hydro Electric Dragon had been created; Nya stated that water and electricity do mix, and Jay responded with a snicker.
Ray and Maya instructed Kai and Nya to use their Elemental Powers to summon the Fusion Dragon. By shooting blasts of their elemental powers towards the Dragon Blade, they were able to do so. Later, they rode the Fusion Dragon back to the Vermillion Base. Kai, Nya and Wu rode the dragon into the Time Vortex.
Just as Acronix and Krux were deciding whether to finish off Wu or Garmadon first, Kai and Nya summoned the Fusion Dragon once more and rode into battle with the Iron Doom. They tried to take the Reversal Blade but failed. The Iron Doom knocked the Fusion Dragon and caused it to steer out of control. The Iron Doom then shot eggs at the Fusion Dragon. Realizing that the Past Reversal Blade was still in the woods, Nya jumped off the dragon. With only one person controlling the Fusion Dragon, it started to fade and Kai began to lose control. Kai slammed the dragon into the Iron Doom, causing it to lose balance. Just as the Iron Doom was about to travel into the future, Kai tried to attack and stop the Iron Doom getting away, but the Iron Doom dodged the attack, causing Kai to fall. Using the Past Reversal Blade, Kai, Nya, and Wu brought back time to when Kai was still on the Dragon. Kai steered it towards Nya and Wu, who leaped back onto the Dragon. They then steered the Dragon into the Time Vortex.
Fusion Dragons are able to harness the original elemental powers from which they were made. They may also be able to use any elements which result from combining those elements (e.g. Energy).
Fusion Dragons may require more energy to sustain as they are made from more than one element. 
- 9450 Epic Dragon Battle (Ultra Dragon)
- 70602 Jay's Elemental Dragon (Hydro Electric Dragon)
- 70627 Dragon's Forge (Water-Fire Dragon)
- 61. "Wishmasters"
- 7. "Beasts and Dragons"
- The Hydro Electric Dragon is the only Fusion Dragon with only one head.
- Nya is the only one that participated in the creation of two fusion dragons.