Idiopathic brachial neuritis is a distinctive condition that occurs most often in healthy individuals. It characteristically starts with an acute unilateral shoulder pain followed by a complex of symptoms, including weakness, paresthesias, and numbness. The cause of this syndrome is unknown and difficult to diagnose in the initial phase but may occur postsurgery, postinfection, posttrauma, or postvaccination. In this case, the patient's inciting event appeared to be a cesarean section. There was no trauma to the shoulder or upper extremity by way of positioning during the procedure. Several months after denervation of the supraspinatus and infraspinatus muscles, electromyography revealed some improvement. The diagnosis was made through a combination of clinical evaluation, ultrasound, magnetic resonance imaging, and electromyography. With the exception of weakness, this patient experienced few symptoms. Treatment is symptomatic including anti-inflammatories, opiates, and neuroleptics for pain. There is some evidence that immunotherapy may help decrease the length of symptoms, but there is no strong evidence to support steroid use. Physical therapy, the foundation of therapy in this case, is a useful adjunct for rehabilitation. In general, this condition has a good prognosis for recovery, although often slow, even when there is complete denervation. This patient made a full recovery and has no lingering symptoms.