Brachial plexus lesions secondary to Herpes zoster is a rare neurological complication. This condition should be kept in mind in the differential diagnosis of acute weakness in the upper extremities. In this case report, we present a 57-year-old female patient, who presented to our clinic with complaints of weakness and pain in the left arm 3 days after the development of a herpetic lesion on the left shoulder and underwent an investigation that revealed a brachial plexus lesion.