Prior to the start of the series, Kingdra was a Horsea owned by Silver when he lived with the Masked Man. After escaping from the Masked Man, Silver gave Green Horsea in exchange for her Snubbull before the two parted ways.
Horsea first appeared in Zap! Zap! Zapdos!, where she battled against Sabrina and her Kadabra. Horsea quickly released a Smokescreen to blind her opponents while Green wore a modified Silph Scope, allowing her to see through the smoke. Despite this, Sabrina was still able to see perfectly fine thanks to her psychic abilities and had Kadabra launch an attack at the Dragon Pokémon. The Psi Pokémon then cleared the smoke with Psychic and used Disable to prevent Green and Horsea from moving. With the help of Jiggly and Clefy, Green managed to escape from the gym leader.
In Cloystered, Horsea fired ink at Lorelei from a distance, distracting the Elite Four member long enough to allow Yellow and Bill to escape from her.
In Playing Horsea, Green had Horsea cover Jiggly in a Smokescreen while she, Yellow, and Bill rode the Balloon Pokémon over Cerise Island. While traveling through the air Bill droped their map, which was found and eaten by one of Lorelei's Slowbros. Green then had Horsea latch herself onto a spike on Slowbro's tail while leaving a trail of ink for her Trainer to follow. Horsea was later found by Lorelei, as she was noticed by the Shellder on Slowbro's tail, and was used as a hostage. Lorelei told Green she can have the Dragon Pokémon back if she and Sabrina came closer. Green followed the order and was knocked unconscious by Lorelei's Jynx's Pound attack.
Sometime after the Yellow arc, Horsea was given back to Silver and evolved into a Seadra. In Ampharos Amore, Silver traded Seadra to Gold for his Polibo while holding a Dragon Scale, causing Seadra to evolve into Kingdra and Polibo to evolve into Politoed. Kingdra was shortly traded back to Silver for Polibo. Kingdra was later used in Silver's battle against Gold. Kingdra was called out to fight against Gold's Sudobo, where she quickly attacked the Imitation Pokémon with Water Gun. Kingdra was then recalled for Silver's Tyranitar, as Silver wanted to end the match quickly.
In Delibird Delivery - 1, Kingdra used Twister to push Gold away from the ice spikes the Masked Man had set up.
In Curious Kingdra, Kingdra used Waterfall alongside Gyarados's Whirlpool and Feraligatr's Surf to help Silver enter the Whirl Islands and locate Lance.
In The Last Battle XI, Kingdra battled alongside Silver's other Pokémon to defeat Will by attacking with Sneasel's Beat Up.
In Storming the Forretress, Kingdra helped slow the descent of the Team Rocket airship alongside the other Pokédex holder's Water-type Pokémon.
In Dealing With A Koffing Fit, Silver arrived at Lance's secret hideout and was soon attacked by a group of Koffing. Kingdra fought alongside the rest of Silver's team to drive off the large horde of the Poison Gas Pokémon.
Kingdra is a resourceful Pokémon, being used for a variety of tasks by Green and Silver, such as hiding Green in a Smokescreen, leaving a trail with ink, and using Twister to push others to safety. As a Kingdra, the Dragon Pokémon is shown to be very serious, often doing her task without objection and with a stern face. With Silver, Kingdra was used in battle mainly for her speed and Water-type attacks.