Desmoid tumors are histologically benign fibrous neoplasms arising from the musculoaponeurotic structures throughout the body. There is similar biological behaviour between benign fibrous proliferations and fibrosarcoma. These neoplasms have the tendency to locally invade and erode adjacent muscular tissue and bone. Within the head and neck area they also tend to encase vital structures. We present a case of a 28-year-old white female with a five-month history of a painful mass in her left posterior cervical triangle who was treated by excisional biopsy of the lesion with preservation of the accessory nerve and post-operative radiation. The histopathologic characteristics of desmoid tumors and treatment of these lesions are also reviewed.