Ulnar nerve entrapment neuropathies, which are the second most common entrapment neuropathies after carpal tunnel syndrome, are most common in the elbow region. Entrapment of the ulnar nerve at the wrist level is rare. Guyon's canal, located medial to the wrist, is a tunnel-shaped fibroosseous structure through which the ulnar artery and ulnar nerve pass. Guyon's canal syndrome refers to the entrapment of the ulnar nerve at the level of the wrist. In etiology; Besides professional habits, many etiological factors such as ganglion, lipoma, bone fracture and AVMs have been reported. It is rare to trap the ulnar nerve at a level that matches the Guyon canal due to mouse use. In this article, we presented a case of ulnar nerve entrapment in the pediatric age group due to prolonged mouse use.