Goh is a ten-year-old rookie Pokémon Trainer who serves as one of the main protagonists of the series. He was born and raised in Vermilion City in the Kanto region. His parents, Camille and Walker, are software engineers, and he also has a grandmother named Halta whom he loves dearly. As a child, Goh spent a significant amount of time alone as his parents were often busy with work, leading him to have few friends. The primary exception was Chloe, a childhood friend he met at a young age. The defining moment of his early life occurred when he was six years old at Professor Oak's Pokémon Summer Camp. During this event, he and Chloe witnessed the mythical Pokémon Mew, an experience that inspired his life's greatest ambition. Another formative childhood event took place during a family trip to Azalea Town, where he befriended a boy named Horace who was searching for the mythical Pokémon Celebi. After the two promised to meet again, Horace failed to appear, a betrayal that caused Goh to further distance himself from forming new friendships for years.

Goh's personality is defined by its contrast with his traveling companion, Ash. While Ash is reckless, headstrong, and driven by a passion for Pokémon battles, Goh is a stylish, cool-headed, and highly intelligent city boy who primarily relies on technology and data analysis. He possesses an extensive academic knowledge of Pokémon species and behaviors, which he uses to aid his research. This intelligence, however, sometimes manifests as an ego or a know-it-all attitude, which can make it difficult for him to connect with others. Despite a confident exterior, Goh is easily flustered and often blushes in social situations. His isolated childhood means he often struggles to understand the feelings of both people and Pokémon, sometimes misinterpreting playful banter as insults or believing a minor argument could permanently end a friendship. He is also known for a hot competitive streak, particularly with Ash, but firmly rejects being labeled as Ash's rival, instead insisting they are friends and equal research partners.

Goh's central motivation is to catch every Pokémon species from every region. This grand ambition is ultimately in service of his primary dream: to catch the mythical Pokémon Mew, the creature that inspired him as a young child. He becomes a research assistant at the Cerise Laboratory in Vermilion City, a role that allows him to travel the world with Ash to study Pokémon and pursue his capturing goal. His role in the story is that of a deuteragonist, sharing the spotlight with Ash. Unlike previous traveling companions who often played a supporting role, Goh's own journey, goals, and character development receive nearly equal focus. He is present for many of the series' major events, including the Darkest Day arc in the Galar region, and eventually joins the Project Mew research expedition as a Chaser, seeking to prove himself worthy of a special mission to find Mew.

His most significant relationship is with Ash. The two boys first met when they both leaped onto the back of the legendary Pokémon Lugia at the same time. Bonding during their shared adventure, Goh immediately accepted Ash as his friend. Their friendship grows as they travel and work together, with Goh coming to admire Ash's determination, his bond with Pikachu, and his unorthodox but effective battling style. Goh often acts as a grounding presence for Ash, and in turn, Ash helps Goh become more open to socializing and trusting others. Goh's long-standing friendship with Chloe is also central. Though she is often exasperated by his antics, their bond is deep and they consistently support each other. Through Chloe, Goh also has a long-standing connection to Professor Cerise, who acts as a mentor figure. His relationship with his Pokémon is a major part of his development. His first partner was a Scorbunny he met in the Galar region. Initially, Goh was more focused on catching Pokémon than bonding with them, and he was overly cautious about his Scorbunny training too hard, leading to a strain in their relationship. Over time, Scorbunny evolved into Raboot and then Cinderace, and Goh learned to better understand and support his partner's desire to grow stronger, though his journey with Raboot included periods of emotional distance and reconciliation. He later also developed strong bonds with other Pokémon, including Inteleon and Grookey.

Goh demonstrates significant development over the course of the series. He begins as a socially awkward, somewhat arrogant boy who prefers the company of data and research to people. His experiences traveling with Ash, caring for his Pokémon, and interacting with a wider world slowly teach him empathy, humility, and the value of friendship. He learns that battling and emotional bonds are essential parts of being a successful Trainer, moving away from his early strategy of simply throwing Poké Balls without combat. His journey culminates in his growth from a solitary researcher into a capable and caring Trainer ready to pursue the most challenging goal of his life with Project Mew.

In terms of abilities, Goh possesses several notable traits. His most distinctive skill is his talent for catching Pokémon, which he often does by throwing a Poké Ball without weakening the target first, a method reminiscent of the gameplay in Pokémon GO. He is extremely knowledgeable and a skilled researcher, adept at gathering and analyzing information using his Rotom Phone. While intelligent, he sometimes dislikes doing homework and skips school. His athletic abilities are inconsistent; he can run reasonably well but struggles with climbing, swimming, and other physical challenges. As a battler, he starts off inexperienced and overly reliant on textbook type matchups and stat boosts, but he gradually learns to adopt more creative and unpredictable tactics by observing Ash. He is also left-handed and receives a Dynamax Band during the Darkest Day arc, which allows him to temporarily Dynamax his Pokémon in specific energy-rich locations like the Galar region.