Hamtaro is a male golden hamster who serves as the central protagonist of his anime series. He lives with his owner, a young girl named Laura Haruna, in a typical family home. Hamtaro is characterized by his boundless curiosity, playful energy, and an optimistic outlook on life. His primary motivations are to make new friends, help those in need, and have fun adventures every day. He approaches each new situation with enthusiasm and a genuine desire to assist others, often going out of his way to solve problems for both his fellow hamsters and his human owner.

In his role within the story, Hamtaro is the heart of the group. He is the one who, after moving to a new neighborhood, ventures outside his home and begins meeting other pet hamsters. It is his idea to transform an elaborate underground burrow, owned by a hamster named Boss, into a clubhouse where all the hamsters can gather, known as the Ham-Ham Clubhouse. He naturally assumes the role of an unspoken leader, not through authority, but through his courage, selflessness, and ability to unite his friends to overcome challenges. He is consistently portrayed as brave, as shown when he rescues the young hamster Penelope from a cat, and is always ready to lend a paw, whether to help a friend in distress or to cheer on someone pursuing a dream.

Hamtaro's key relationships form the core of his world. His bond with his owner, Laura, is one of deep affection and loyalty. He is often visibly upset when he feels ignored by her and takes an active interest in her life and happiness. Among the other hamsters, his best friend is Oxnard, a large, food-loving hamster who was the first friend he made after moving. He shares a brotherly connection with Oxnard. Hamtaro also looks up to Boss, who is older and often wiser, treating him with respect even when Boss shows jealousy over the affections of other hamsters. A significant dynamic exists between Hamtaro and a female hamster named Bijou. Bijou has a clear crush on him, but Hamtaro, due to his innocent and naive nature, is almost completely oblivious to her romantic feelings as well as those of several other female hamsters. He treats all his friends with the same kind and caring attitude, never distinguishing between a potential romantic interest and a platonic friend. He shares mutual respect with other members of the Ham-Hams, including the inventor Dexter, the joker Howdy, the knowledgeable Maxwell, and the sleepy Snoozer.

Throughout the series, Hamtaro does not undergo a drastic personality change, but he does demonstrate subtle development through his experiences. He continues to show growth in his courage and problem-solving skills as he faces various adventures, from reuniting lost siblings to navigating the temporary dissolution of the clubhouse when Boss departs on a journey. His core traits of optimism, loyalty, and kindness remain steadfast, even as the storylines evolve to include magical or more complex scenarios. Hamtaro also possesses several notable abilities. Beyond his general bravery and quick thinking, he has a unique way of communicating, often punctuating his speech with playful exclamations like Hamha! in many language versions. He is also physically adept for his small size, capable of running quickly, digging, and using his paws to manipulate objects in a way that resembles human hands. His most defining ability, however, is his talent for bringing other hamsters together, fostering teamwork and camaraderie to achieve a common goal.