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.

One day, while listening to Laura and Kana plan an evening barbecue, Hamtaro becomes enchanted by what the girls are eating--a sparkling candy called “Diamonds of Sugar”. Puzzled, Hamtaro goes to the Ham-Ham Clubhouse to ask his friends if they’ve heard of these "diamond things". After many theories from the hamsters, Boss insists the candies come from the sky and are best seen at night.

Laura's parents take her on her first trip to the beach; but when they tell her that the water can be dangerous for hamsters, she decides not to take Hamtaro. However, Hamtaro and the Ham-Hams have other ideas! They want to see the ocean, so they make a plan to go to the beach too, after agreeing that if they stick together, they can look out for one another.

It's a summer festival! The Ham-Hams learn from Maxwell that on the night of the festival, flowers (fireworks) will appear in the sky. Pashmina separates from the Ham-Hams to find the flowers.

Hamtaro goes with Laura and her family to visit her grandmother in the country. The Ham-Hams are excited for Hamtaro, because Grandmother's house is surrounded by sunflower fields.

After Laura begins a new semester, the Ham-Ham pals start to wonder if they might be missing something by not going to school. After Hamtaro, Oxnard, and Boss sneak into Laura's school for a day to check things out, the Ham-Hams set up a separate school of their own.

Laura's father asks her to deliver an important floppy disk to his office. While Laura packs her bag, Hamtaro gets trapped inside. On the way to Mr. Haruna's office, Hamtaro picks up two hitchhikers, Oxnard and Penelope, who have just escaped from an angry crow. When Oxnard's sunflower seed falls to the ground, Oxnard jumps out of Laura's bag to go after it, and Hamtaro and baby Penelope follow, not knowing that the yellow disk has slipped out of Laura's bag too.

It's Grandparents Day, and when Grandma comes for a visit she shows Laura an old clock that she and her friend, Kaitlyn, bought years ago. Laura is touched by the story and decides to surprise her grandmother by trying to find her long-lost friend for her.

When Laura and Kana go shopping, the Ham-Hams go along, but soon find danger in the shopping district. Bijou wanders down a nearby alley, but she doesn't return!

As Elder Ham's Sunflower Seed Harvest Festival approaches, Sandy confesses to Hamtaro that she has a crush on Maxwell because he reminds him of her brother. Sandy asks Hamtaro to find out if Maxwell feels the same about her.

Picking up where the last episode left off, Hamtaro and Oxnard locate Sandy's twin brother, Stan, and bring him back to the Clubhouse. To celebrate, the Ham-Ham gang decides to throw a surprise reunion party for Sandy.

In a game of Blind Man's Bluff, Cappy takes Bijou's ribbon on accident, but Hamtaro gets the blame. To make it up to her, everyone plans a trip to Acorn Mountain and collects some acorns to help her feel better.

Laura's gone down with a cold, and Hamtaro feels terrible about her condition because he kept running on his wheel all night. Meanwhile, Boss develops a "stomach-ache" and Maxwell steps in to help cure him with yogurt found in Laura's fridge.

All of the Ham-Ham's special items have suddenly gone missing! Luckily, Hamtaro is on the case and wants to know what's going on and who really had an intent on stealing everyone's things.

When Laura is asked to perform the role of Cinderella in the school play, the nervous actress accidentally leaves one glass slipper at home. When Hamtaro discovers the lost slipper, he and his Ham-Ham friends set out to secretly deliver the slipper to the theater.

Despite Boss, Howdy and Stan's stubbornness, the Ham-Hams decide to build a fun park under Panda's leadership. Meanwhile, Laura's family goes to the amusement park, but the car machinery breaks down.

During spring-cleaning at the Clubhouse, the Ham-Hams can’t wake up Snoozer, so they haul him outside on a table and leave him with the rest of the furniture. Then a remote-control car, powered by two boys, crashes into the desk and carries him away. In the meantime, Snoozer’s drowsy personality sparks some discussion among the Ham-Hams who realize that they don’t really know who their sleepy friend is.

Admiring his courageous and heroic background, Cappy decides that he wants to become a field hamster just like Boss, and the Ham-Hams are worried about him losing his home life with his owners, Kip and Sue.

Today is Travis' birthday, but Laura's having a hard time finding the perfect gift to give for him on that special day. Hamtaro, with the same idea in mind, declares a competition with Pashmina as the judge to see who can give her the best gift.

Maxwell decides to create a newspaper called "The Ham-Ham Times" after Hamtaro learns that Laura and Kana are making a newspaper for the school. The Ham-Hams set out to each find news worthy of the paper.

While on a walk with Laura, Hamtaro falls into a box on a transport truck in an attempt to save one of Laura's ribbons and is taken away. Laura becomes very distraught. The Ham-Hams become determined to start searching for Hamtaro.

It's Christmas time! Boss and Snoozer want to get a gift from Santa. The Ham-Hams decide to help and everyone gets gifts from the hamster-Santa. Meanwhile, Laura wants a dollhouse for her gift.