The spinal accessory nerve can be injured as a complication of various surgical procedures or traumas. The surgical procedures which may injure the accessory nerve are biopsy of lymph nodes, operations involving the neurovascular structures and resection of a tumour in the posterior triangle of the neck. The purpose of this case report is to describe the management of a 31-years woman with spinal accessory nerve injury following a biopsy of a tumour. Electromyography and faradic excitability tests demonstrated evidence of denervation in the trapezius. A decrease in the range of motion of the neck and shoulder, and sharp pain of acute onset and hyperaesthesia were the initial symptoms on the side of the surgery. Superficial heat, TENS, scapular and glenohumeral joint mobilisation, range of motion of the neck and shoulder and posture exercises were applied three times a week. After three months, the patient had regained normal functions of the neck and shoulder and had no symptoms even when lifting heavy objects or performing overhead activities.