Jam Ojisan, also known as Mr. Jam, is the kind and warm-hearted primary baker and creator of Anpanman. He appears as an elderly figure with gray hair, fluffy eyebrows, a mustache, and lighter red cheeks and nose compared to Anpanman. His attire consists of a white chef's hat, white shirt and pants, a white apron, and bluish-gray shoes.

Deeply caring and paternal, he strives to help everyone. His extensive knowledge from youthful travels fills the many books in his bakery. Beyond baking, he is a skilled mechanic capable of building and repairing mecha machines like the Anpanman Mobile, fixing robotic characters, and riding motorcycles. His inventor and researcher background implies other unshown abilities.

Jam Ojisan created Anpanman when a "star of life" landed in his oven during an anpan bake. Raising Anpanman from infancy forged their father-son bond. He also created Melonpanna, Rollpanna, and possibly Currypanman—though the latter's origin was later retconned. He resides in the bakery with Batako, his unrelated assistant; their close familial connection possibly dates to infancy. He cares for Cheese, the pet dog Anpanman rescued as a puppy. Acting as a father figure to Melonpanna and adoptive parent to Creampanda, he encourages their growth. Due to Rollpanna's "evil blue heart," they maintain distance, though he repeatedly invites her to join the bakery.

In episodes like "Jam Ojisan to Jam Baikinman" and "Jam Ojisan no Himitsu," he interacts with Baikinman disguised as "Jam Baikinman" and faces challenges. Stories such as "Jam Ojisan to Arigatou no Hi" and "Jam Ojisan to Magomajo" further explore his role in conflict resolution and support.

A theory notes that neither he nor Batako are human but "fairies," as humans do not exist in the Anpanman World. Early depictions in the 1973 picture book and manga showed him smoking a pipe, omitted in later adaptations. Initially unnamed, he was generically called "uncle" or "old man."