Malignant tumors in the lacrimal sac are relatively rare. The symptoms are similar to chronic dacryocystitis, and so treatment is often delayed. We encountered two patients, an adenocarcinoma case and a squamous cell carcinoma case, who received treatment for chronic dacryocystitis. Both cases underwent partial maxillectomy with orbital clearance. The adenocarcinoma case had local recurrence, underwent chemoradiotherapy, and survived with no evidence of disease. The SCC case underwent adjuvant chemoradiotherapy and survived with no evidence of disease. The principal treatment for lacrimal sac cancer is surgical removal. A multidisciplinary approach should be considered according to the histological types and extent of disease.