Subacromial impingement syndrome is a frequent cause of shoulder pain and it is readily confused with other shoulder problems. We present a patient with herpes zoster infection associated with axillary mononeuropathy that was initially misdiagnosed as subacromial impingement syndrome. A 75-yr-old female patient was admitted to the internal medicine clinic because of pain and weakness in her right shoulder. As she did not respond to medical treatment and local injection therapy, magnetic resonance imaging of the right shoulder was ordered. As the magnetic resonance imaging revealed subacromial impingement of the supraspinatus tendon, the patient was referred to the physical medicine and rehabilitation department for rehabilitation. In our initial physical examination, her shoulder abductor muscle strength was 2/5 and her shoulder external rotator muscle strength was 3/5. A subacromial injection test with 10 ml of 1 % lidocain was negative and the magnetic resonance imaging did not show a complete rotator tendon rupture that could explain such a muscle strength loss. So, an electrodiagnostic evaluation was performed and the patient was diagnosed to have a right axillary neuropathy. A more detailed questioning of the patient disclosed a history of herpes zoster approximately 3 mos ago. Herpes zoster-associated axillary neuropathy can mimic subacromial impingement syndrome, and magnetic resonance imaging examination alone may lead to a misdiagnosis. Therefore, we imply that clinical and electrophysiological evaluations would be of great importance in relevant patients with shoulder problems.