Brandon's Registeel first appeared in Overjoyed, where it battled Ash's Torkoal. Despite type disadvantage, Registeel won, although it was exhausted by the end of the battle. It later appeared to get rid of Team Rocket, along with Regirock whilst Brandon was battling Ash.
During A Pyramiding Rage, Registeel battled Paul's Magmar and caused it to flinch by using Iron Head so Paul recalled it. Registeel then battled Nidoking, enduring Earth Power, Double Kick and Thunderbolt, whilst striking Nidoking with Flash Cannon and knocking it out with Iron Head.
Registeel also battled Regigigas and then went on a rampage when it was affected by Confuse Ray. It then defended Regigigas from Pokémon hunter J and after J abandoned her attempt to catch Regigigas, Registeel, Regirock, Regice and Brandon decided to stay at Snowpoint Temple.