In the film, Pachirisu serves as one of Dawn's Pokémon companions. When dimensional disturbances erupt from the clash between Dialga and Palkia, Pachirisu actively contributes to defending Alamos Town. Alongside Dawn's other Pokémon, it helps divert a rampaging Metagross and Magnezone away from populated areas, minimizing damage during the evacuation.

During the climax, Pachirisu undertakes a critical task: activating the Space-Time Towers' instrument. After Darkrai immobilizes Dialga and Palkia, the towers require an electrical charge to play the "Oración" melody. Pachirisu joins forces with Ash's Pikachu, combining their electrical powers to energize the towers. This combined effort successfully broadcasts the song, calming the enraged legendary Pokémon and restoring peace.