The stinger syndrome is a common neuropathy caused by traction or compression of the brachial plexus. In general, it is seen in young adults involved in sport activities and a major contact trauma is the rule. An 11-year-old boy with bilateral glenohumeral joint laxity had pain in the left shoulder, numbness and decreased strength in the left arm that developed after striking against a wall while running, with the left shoulder in extension and the neck in minimal lateral flexion to the contralateral side. Physical examination showed extreme anteroinferior passive translocation of the humeral head in neutral rotation and a positive sulcus sign in the left shoulder. The diagnosis was made as brachial plexus neuropathy (stinger syndrome) resulting from traction trauma and shoulder joint laxity and a shoulder-arm brace was applied. After two weeks, atrophy was detected in the right deltoid, supraspinatus, and infraspinatus muscles, and active and passive motion exercises of the shoulder were initiated. At the end of three months, he achieved normal range of motion of the shoulder and muscle strength.