Liposarcoma is a common soft tissue malignant tumor, although it is rare in the head and neck region. In particular, there have been only a few cases of liposarcoma arising in the retropharyngeal space. Those tumors cause special diagnostic and therapeutic difficulties. In this case, a well-differentiated liposarcoma of the retropharyngeal space in a 51-year-old woman is reported. The tumor continued to grow slowly over a period of four years. We were unable to make a proper diagnosis of this tumor prior to surgery although the radiographic findings resembled the tumors containing fatty component. In the present case, total excision of the tumor with free margins was performed. Although surgical excision with a wide margin is appropriate, it was difficult to resect the tumor completely. Herein, recommendations for earlier and correct diagnosis and treatment of this neoplasm are discussed with a review of the literature.