Ash first encountered Dragonite as a Dragonair. Unlike the other Dragonair on its home island, it had trouble learning how to fly and use Dragon Dance. Seeing this, Ash offered to help Dragonair master the use of its wings. With an Electroweb trampoline provided by Pikachu, Ash eventually managed to help Dragonair to learn to fly and master Dragon Dance. Dragonair then sensed that one of its Dragonite friends was in trouble and led Ash and Go to it. It turned out that Team Rocket had captured the Dragonite, and sent out a Wailord to deal with the Ash and Go. One of Wailord's splashes sent Ash flying into the air, and Dragonair tried to save him. However, its skin was too slippery for Ash to hold on to, so it then proceeded to evolve into Dragonite and save Ash from the fall. After Team Rocket had been defeated, Dragonite expressed its willingness to come with Ash, so he caught it.
Capture of a fully evolved Pokémon from an evolutionary line since Beedrill in The Bug Stops Here, 934 episodes before Dragonite's capture, and thus also his first such capture outside of the original series.