The Siberian mouse is a relatively small rodent, measuring approximately 10-14 cm (4-6 inches) in length, with a tail of about 6-8 cm (2.5-3 inches). Its fur is thick and soft, with a grayish-brown color on the back and white underside. The most distinctive feature of this mouse is the dark stripe that runs along its back, from the head to the base of the tail. This stripe can be brown or black, and it helps to distinguish the Siberian mouse from other similar species.