Liposarcoma is a soft tissue neoplasm that commonly develops in the lower extremities and rarely in the head and neck region. Herein, we report the case of a patient with primary liposarcoma that was detected in the mastoid antrum during staged tympanoplasty for cholesteatoma. The tumor adjacent to the attic cholesteatoma was resected completely, and the pathological diagnosis was that of myxoid-type liposarcoma. Because positron emission tomography after the surgery showed no signs of tumor remnants or systemic metastasis, a second-stage surgery was performed 8 months after the first surgery. After confirming that there was no recurrence, tympanoplasty type III with interposition between the stapes and malleus and canal reconstruction was performed. No recurrence was observed for 5 years, and to date, good hearing has been maintained. This is the first report on long-term follow-up of a patient with liposarcoma in the mastoid antrum.