Brock is the first Gym Leader. He serves at the Pewter Gym as a current gym leader. A Rock type Pokémon trainer, he is seen using Geodude, Sandshrew, and Onix.
- Pewter Gym
- Jessie and James report back to Brock, turning over all of the Rare Candy and Pokémon they took. They also bring Joey along to Pewter Gym, where Brock feeds the Rare Candy to his Onix. When the Player arrives, Brock's Geodude and Camper Luigi's Sandshrew try to steal back the Pokeballs. After that fails, Brock sends in his Onix.
- Route 3
- Mt. Moon 1
- Mt. Moon 2
- Cerulean Gym
- After sending the wild Pokémon stampeding through the cave in Mt. Moon 2, the Pokémon make the rocks fall and Brock gets trapped in the cave with Jessie and James. A wild Abra randomly teleports into the cave due to Joey trying to Body Slam the Abra, and Brock with Jessie and James use it to escape.
- Vermillion Gym
- Diglett's Cave
- Viridian Ending
|Onix||Defense Curl, Rock Throw|
|Mewtwo (Gives to Sabrina)||Amnesia, Barrier, Psychic, Psycho Cut, Recover, Teleport, Nasty Plot|
- In Mt Moon 1, when Pikachu Sammy uses his electric attack, Brock notes that the attack was not very strong. This is a reference to when he travelled with Ash, and Ash's Pikachu used to shock everyone, with significantly stronger power.
|Ash Ketchum • Gary Oak • Joey • Mewtwo • Maruto|
|Mewthree • James • Jessie • Meowth • Jerry • Tom • Giovanni|
|Brock • Misty • Lt. Surge • Erika • Sabrina • Janine • Blaine • Gary Oak|
|Professor Oak • Camper Luigi • Cal • Bug Catcher • Old Man • Kyogre • Bill • Celebi • Bruno • Sam • Sensei • Groudon • Lorelei • Koga • Lance • Mew|