Lunate and perilunate dislocations are uncommon, but they have clinical importance because complications, such as median neuropathy and avascular necrosis of the lunate, can occur. Although early diagnosis enabling early surgical treatment is crucial for preventing long-term sequelae, these dislocations are frequently missed in the initial assessment. Imaging tools, such as plain radiography, magnetic resonance imaging, ultrasonography, and electrodiagnostic studies, have been used for diagnosis. The proper choice of initial evaluation tools is important for making an accurate early diagnosis. Here we present a case of lunate dislocation associated with median neuropathy in which ultrasonography, along with the electrodiagnostic study and plain radiography, played an important diagnostic role in detecting structural abnormalities. This case report reveals the complementary diagnostic role of ultrasonography in initial assessment and provides ultrasonographic images of lunate dislocation as a cause of median neuropathy.