Brock wanted to be the greatest Pokémon Breeder (he is now following his destiny as a Pokémon Doctor), and gives up his title of Gym Leader after Ash won his first Kanto League Gym Badge from him. He was first seen taking care of his nine siblings.
After Ash loses to Brock, a stranger (Brock's father) offers to help make his Pikachu stronger. Pikachu (after being hooked up to a local hydro-power station) becomes stronger and manages to defeat Geodude, but Onix remains too strong. Onix has Pikachu in a body bind; however, Pikachu's previous electric attack ravaged the gym, which set off the sprinklers, weakening his Onix. Ash declines the badge on the grounds that he unfairly beat Brock, but Brock later catches
up to him and presents to him the badge, saying that he wants Ash to fulfill his dream of becoming the best. The stranger that first helped Ash reveals himself to be Brock's father, Flint, who has a tendency to not notify people it is him. Brock is now free to train himself, and joins Ash and Misty on their journey.
Since then, he travels with Ash and Misty on his many adventures. In the Orange Islands series, he leaves the team to join Professor Felina Ivy, but mysteriously returns to Pallet Town when Ash wins the Orange League Championship. When asked what happened, Brock just rolled up into a ball and replied: "I don't wanna talk about it." or "Don't mention that name." every time someone mentions Professor Ivy. Rejoining Ash and Misty, Brock travels to Johto, where he continues to help Ash and Misty. Upon the conclusion of the Silver Conference, the three part ways, Brock heading back to Pewter City. It is there (in an episode of Pokémon Chronicles) that he discovers his estranged mother Lola (Mizuho in the original), who, because she is a Water-type Pokémon Trainer, has ruined the reputation of the Gym he defended so long ago and had ended up filling the gym with water (causing Brock to comically freak out and keeps repeating "A LAKE!!!" when he first sees it).
By defeating his mother, he restores the Gym's reputation, and proceeds to leave all his Pokémon (except Forretress) to his younger brother Forrest, before departing for the Hoenn region, where he catches up with Ash and his two new friends, May and Max.
The group travel across Hoenn and then return to Kanto to participate in the Battle Frontier. The group went their separate ways and Brock met up with Ash in Sinnoh. While there, they meet a new coordinator named Dawn and her partner Piplup, who joins them on their journey through Sinnoh .
During this time, both Brock's father, Flint (Munō in the original, who was also Brock's predecessor as Gym Leader), ran off again, and his oldest younger brother Forrest (Jirō in the original) took the role of Gym Leader in Pewter City, as well as the responsibility of caring for his many other younger siblings. Brock is the oldest of ten siblings, with five brothers and four sisters.
Brock is always well-equipped, and is sometimes the voice of reason when Ash and Misty (and later, May and Dawn) get into an argument. He is also hardworking and is always willing to help others. Coupled with his experiences in taking care of others, Brock often prepares food and does most of the chores for the main characters. Brock is also exceptionally good at making food for Pokemon.
At the end of the Pokémon: Diamond and Pearl series, Brock aspires to become a Pokémon Doctor, and work alongside Nurse Joy. After departing from Ash and Dawn, Brock returns home to Pewter City to train to become a Pokémon Doctor.
In the Pokémon: Diamond and Pearl Special Episode 2, he has photos of Ash, Misty, May, Max, Dawn, Piplup, and Pikachu to remind him of how much fun it was traveling with them. He also chooses his brother Forrest to replace him as Gym Leader
In the Black and White Special he encounters Cilan in a small town. He helps treat Pansage after it got hurt fighting a Gyarados. The two form of fast friendship and work together as they help Gyarados. As they part they both realize they never asked for each others name.
- English: Eric Stuart (Seasons 1 - 8, Movies 1 - 8) (4kids)
- English: Bill Rogers (Seasons 9 - present, Movies 9 - 13) (PUSA/DuArt)
- Japanese: Yuji Ueda
- German: Marc Stachel
- Dutch: Fred Meijer
- Italian: Nicola Bartolini Carrassi (Season 1 - 2); Luca Bottale (Season 3 - 13)
- Greek: Charis Grigoropoulos
- Brazilian Portuguese: Alfredo Rollo
- Swedish: Mattias Knave
- Arabic: Rafat Pazo
- Bulgarian: Alexander Voronov
- Mandarin: Fu Shuang, Liang Xingchang, Yu Zhengsheng
- Finnish: Jari Salo, Juha Paananen
- Korean: Ku Ja-Hyeong, Byeon Yeong-Hyi
- Croatian: Igor Mešin
- Danish: Peter Holst-Beck
- Czech: Martin Pisarik, Jan Maxian, Michal Holan, Jiri Balcarek
- French: Laurent Chauvet (Season 1-8), Antoni Lo Presti (Season 9-13)
- Norwegian: Eirik Espolin-Johnson, Erik Skold
- Filipino: Julius Figueroa
- Hebrew: Guy Roshiniak
- Polish: Marek Wlodarczyk (Season 1-9, 11-13), Waldemar Barwinski (Season 10)
- Hungarian: Sotonyi Gabor
- Canadian French: Martin Watier
- Portuguese: Peter Michael (Season 1-2), Rui Quintas (Season 3-9), Luis Barros (Season 10), Pedro Almendra (Season 11-13), Vitor Emanuel
- Indonesian: Dicky Rahman (Season 1-2), Dendry Patma (Season 3-10), Kamal Nasuti (Season 11-13)
- Russian: Dimitrii Zavatskii
- Spanish: Javier Balas, Sergio Sanchez
- Thai: Nirand Bunyaratpan
- Latin America Spanish: Gabriel Gama (season 1 - 10,13-present), Jose Antonio Macia (one scene of EP164), Alan Prieto (season10-12), Arturo Mercado Jr (Movie 4-5).
- Turkish: Tugay Erverdi
- Pokemon Wiki