Hamtaro, the curious pet hamster of 5th grader Laura Haruna, sets out to meet the neighbors after they move to a new town. While Laura enjoys a snack with her parents, Hamtaro sneaks out of his cage and down the drainpipe. Once outside, he meets his hamster neighbor Oxnard, who is looking for his missing sunflower seed. Hamtaro helps him find it and they declare each other friends afterwards.

On Laura’s first day of school, Hamtaro can't help Laura choose the perfect outfit, but he decides to help by keeping an eye on her at school. He soon gets sidetracked though when he runs into his new friends Oxnard and Boss, who introduce him to more hamster pals, Pashmina, Penelope, Howdy and Dexter.

Since the opening of the Ham-Ham Clubhouse, Hamtaro is meeting new hamsters every day. Pashmina and Penelope introduce their friends Maxwell, Panda and Sandy. Cappy also sneaks up on them under a saucepan, and they become friends. But with all the new Hamsters come Ham-personalities that clash. One day when this happens, a fed-up Boss kicks everyone out the clubhouse.

Boss is cleaning the Clubhouse to invite Bijou over. He, Hamtaro, and Oxnard go visit Bijou to persuade her to come. She refuses, because she has never been outside of her cage, and her owner would be worried when she finds out she's gone.