Empoleon first appeared as a Piplup in Stagestruck Starly, as one of the three Pokémon given to Platinum from Professor Rowan.When Platinum started her journey, she chose Piplup as her starter Pokémon and let her out of her Poké Ball.
In Putting a Crimp in Kricketot, Platinum was attacked by a group of wild Kricketot and Kricketune, forcing Piplup to defend her. Despite her best efforts, Piplup was unable to defeat them entirely, dealing a huge blow to her pride. In an attempt to regain her self-respect Piplup insists that her and Platinum challenge the local Gym Leader Roark. In order to prepare Piplup trains with Tru and Chimler to prepare. The next day, Piplup faces off against Roark's Cranidos at the Oreburgh Gym, but is hurt by a powerful Shock Wave and is forced to be sent back. After Ponyta falls to Roark's Onix, Piplup is sent back out and quickly defeats it with a Water-type attack. With some advice from Diamond and Pearl's comedy routine, Platinum commands Piplup to use Water Pulse, which confuses Cranidos and causes it to knock itself out, giving Platinum the victory and allowing Piplup to regain her pride.
In Ring Around the Roserade I, after leaving the Old Chateau the group meets Gardenia, who somewhat nudges them into challenging her the next day. The three soon begin training with the starter Pokémon when Cynthia walks by and notices that the three are going to evolve. Quickly after saying this the three evolve, with Piplup evolving into a Prinplup.
In Ring Around the Roserade II, Prinplup was used in Platinum’s double battle alongside Ponyta against Gardenia and her Roserade and Cherubi. Despite the type advantage Ponyta was quickly defeated due to Roserade's poison thorns, leaving Prinplup to battle by herself. Due to the distance Gardenia put between them Prinplup continues getting pummeled by both Cherubi and Roserade and being unable to counterattack. This quickly changes as Platinum takes advantage of the holes made in the ground by Grass Knot and uses that to direct a hidden Blizzard at both Roserade and Cherubi, knocking them out cold.
In Perturbed by Pachirisu, Platinum and Prinplup enter a Pokémon Contest. Due to several saboteurs working against them, Platinum and Prinplup lose their confidence and consider quitting. However, with words of encouragement from Diamond, they gain enough confidence to continue going on and manage to win the contest.
In Great Gible, it is revealed that Prinplup evolved into an Empoleon.
In Crafty Carnivine, Empoleon is used as Platinum's first choice in her battle against Crasher Wake and his Floatzel. The two exchange a few blows before moving the battle to the waters. Empoleon manages to easily beat Floatzel with a Vacuum Wave and then goes up against Quagsire. The two fire Blizzard at each other and it appears to be even, but due to tiring herself out from the last battle Quagsire overpowers her and wins, knocking her out.
In Mirages of Mismagius I, Empoleon is used in Platinum's next Gym battle and faces Fantina's Drifblim. Empoleon manages to win by freezing its Ominous Wind with Blizzard, which spread to Drifblim and froze it. She then fought Mismagius and lost quickly due to its illusion powers. In Brash Bronzong I, when Platinum goes to find her kidnapped father, she uses Empoleon against the Gym Leader Byron, who she believed to be the perpetrator. Empoleon manages to damage Byron's two Bronzong but is defeated by a Payback attack.
As a Prinplup after winning a Contest
In Striking Out Snover, Empoleon is used in Platinum's battle against Candice, fighting against her Snover. With a powerful Metal Claw Empoleon quickly defeats Snover, but is soon knocked out by Snover's Seed Bomb which it fired earlier, resulting in a tie.
In Shorting Out Electivire, when Platinum was trying to convince Volkner to train her, Maylene, and Candice, Empoleon was used against his Raichu. Even though she managed to trap it in ice with Blizzard, Raichu managed to free itself with a Berry and defeated Empoleon with Thunderbolt. After Volkner accepts, Empoleon was used to battle his Electivire and manages to win, earning Platinum her final Badge.
In Getting the Drop on Gallade I, Empoleon is used in Platinum's Battle Castle challenge and is used against Darach and his Gallade. Empoleon uses her speed to get behind Gallade and hold him still, but he extends his blades behind him and deals heavy damage, making Platinum recall her. She is later switched back in to fight his Houndoom and defeats it with a Hydro Pump. After that Staraptor is called out and after a tiring battle Empoleon beats it with Blizzard. She is then switched back in again and later called out to finishes off the Attract-inflicted Gallade with Drill Peck, giving Platinum her first Battle Frontier win.
In Exit Empoleon, Platinum used Empoleon in her Battle Arcade challenge. During the battle against Arcade Star Dahlia, Platinum and Dahlia had to switch Pokémon due to the roulette, meaning Empoleon and Platinum's other Pokémon were forced to fight against their Trainer. Although both sides were reluctant at first, both Platinum and her Pokémon manage to fight at their full strength, which eventually ended with Platinum as the victor.
When Platinum went to challenge the Battle Factory, she sent Empoleon and her other Pokémon to search for Looker on Stark Mountain, who had gone missing. They soon return, heavily injured and exhausted with a similarly injured Looker and Buck.