Primary lacrimal sac tumor is relatively rare and is often misdiagnosed as chronic dacryocystitis, thereby delaying its treatment. We encountered a patient who underwent partial maxillectomy, orbital clearance, parotidectomy, modified neck dissection, and reconstruction with rectus abdominis flap. A multidisciplinary treatment comprising surgery, chemotherapy, and radiotherapy is generally recommended for primary lacrimal sac tumor. In addition, the primary lacrimal sac tumor needs to be treated according to various histological types such as squamous cell carcinoma, undifferentiated carcinoma, and transitional cell carcinoma. Because tumor recurrence is often observed after a long time, long-term follow-up is considered necessary. When examining patients with lacrimation or swollen lacrimal sac, we recommend that primary lacrimal tumor should be considered in differential diagnosis for early diagnosis.