Piplup, Dawn's Water-type Pokémon and primary partner in "Pokémon: Arceus and the Jewel of Life", accompanies Ash, Brock, and Dawn to Michina Town. Near a riverside, the group encounters watermelons floating downstream, later identified as belonging to residents Kato and Kiko. Piplup participates in a tag battle alongside Ash's Pikachu against Kato's Heracross and Kiko's Beautifly, actively contributing to the victory before sharing the watermelon with the group and their Pokémon.

When a spatial distortion opens near the river, generating a vortex that threatens Pikachu and Piplup, both Pokémon struggle against the suction force. Piplup employs its BubbleBeam move to resist the pull. Dialga, summoned by Sheena, intervenes to rescue them and seals the distortion with Roar of Time.

Piplup remains present during Giratina's enraged appearance and subsequent confrontation with Dialga, Palkia's arrival to assist against another distortion, and Sheena's explanations regarding Arceus, the Jewel of Life, and dimensional disruptions. It witnesses Arceus's arrival in Michina Town and the destruction caused by Arceus's Judgment attack after the offered Jewel of Life is revealed as counterfeit.

As Dialga, Palkia, and Giratina confront Arceus to protect humanity, Dialga sends Ash, Dawn, Brock, and Sheena back in time to rectify the past betrayal of Arceus. Piplup accompanies Dawn on this journey to the ancient past.

Throughout the film, Piplup consistently engages in group activities, battles, and perilous situations alongside Dawn, utilizing its BubbleBeam move during the spatial distortion crisis.