Sealeo was present during the opening of the building, held by Juan. Though Team Rocket tried to steal Juan's Pokémon, Juan's Milotic blasted them away and freed the Pokémon. Later on, Sealeo was used in the Double Battle round of Juan's Gym battle against Ash, fighting alongside Juan's Seaking against Pikachu and Snorunt. Pikachu started off with Thunderbolt, but Juan's Seaking protected Sealeo by using Horn Drill, thus redirecting the attack back to Pikachu. Pikachu tried using Thunder, but Seaking redirected the attack, causing Snorunt to be electrocuted as well. Sealeo launched Blizzard, which froze Pikachu, though Snorunt used Icy Wind and created an ice boulder. Seaking and Sealeo launched Hyper Beam and Aurora Beam to shatter the ice, which allowed Pikachu and Snorunt to mount an attack. While Pikachu evaded Sealeo's Aurora Beam, Snorunt got defeated by Seaking's Hyper Beam. Ash sent Corphish out, while Sealeo and Seaking dived into the pool. Pikachu dodged Sealeo's Aurora Beam, while Corphish grabbed Seaking's horn, who tried using Horn Attack. Seaking repelled Corphish with Horn Drill, but was defeated by Pikachu's Iron Tail. Sealeo, however, used Ice Ball, though Corphish's Harden countered the move. Sealeo repeated its attack, but was crushed by Corphish's Vice Grip. Sealeo repeated the attack for the third time, but was destroyed by Pikachu's Iron Tail. The fourth time Sealeo launched Ice Ball made Pikachu and Corphish wounded by the attack. In the final time, Sealeo used Ice Ball, Pikachu used Thunder and gave his best to crush the ice. Corphish, however, came closer to Sealeo and defeated it with Crabhammer.
Before arriving to Slateport City for May's Grand Festival, she and Ash remembered their past adventures so far. Ash recalled facing Juan, whose Seaking and Sealeo were used in the Double Battle. Pikachu dodged Sealeo's Aurora Beam, but Snorunt took Seaking's Hyper Beam attack. Soon after, Pikachu defeated Seaking with Iron Tail and Corphish defeated Sealeo with Crabhammer.
|Blizzard||The Great Eight Fate!|
|Aurora Beam||The Great Eight Fate!|
|Ice Ball||The Great Eight Fate!|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.