The size of Campbell's dwarf hamster varies depending on its location. For example, eight wild specimens examined from Mongolia showed an average head and body length of , an average hind foot length of long, with a tail length of . In captivity, they are proportionally larger, as commercial pet food and fruits provide more nutrition than food found commonly in the wild. The lips and cheeks have white fur and the rest of the fur around the face can be either grey or brown. A dark and narrow dorsal stripe runs along the center of the back from the nape of the neck to about above the tail. The surface of the hands and feet are white to ensure the animal stays warm in colder climates in countries such as Mongolia.