Brock was the Gym Leader of the Pewter Gym but during his travels abroad, his family has taken over the gym in his absence. Brock goal is to become a Pokémon Breeder and learn as much about Pokémon as he possibly can. Brock was impressed with Ash during their first encounter when Ash challenged him to a Gym Battle. Brock decided to journey with Ash and together they have explored many regions including: Kanto, the Orange Islands, Johto and Sinnoh. After their journey in the Sinnoh region, Brock decided to part ways with Ash and pursue his studies to become a Pokémon Doctor.

Brock is also known for his obsession with girls. Almost every girl Brock sees, he immediately falls in love with. Misty, Max and most recently his Pokémon Croagunk have always been there to keep him in check before scaring off the girls with his overbearing introductions. He is also an expert on Nurse Joy and Officer Jenny as he recognizes all the differences in their personalities and features where as other people cannot tell the difference.

While on Valencia Island, Brock met Professor Felina Ivy and was instantly attracted to her. He got to know her and decided to stay and help around the lab with the housework and be an assistant for her Pokémon studies. He stayed with her and the triplets for awhile until he left them and reunited with Ash and Misty in Pallet Town. Brock never really explained the reason he left but whenever someone would bring up Professor Ivy, he would go into a shocked and scared shell state.