Lacrimal sac tumors are rare tumor types, with a long time interval from disease onset to diagnosis. We aimed to investigate the characteristics and outcomes of patients with lacrimal sac tumors. The medical records of 25 patients with lacrimal sac tumors initially treated at the Kyushu university hospital from January 1996 to July 2020 were reviewed. Our analysis included 3 epithelial benign tumors (12.0%) and 22 malignant (88.0%) tumors (squamous cell carcinoma, n=6; adenoid cystic carcinoma, n=2; sebaceous adenocarcinoma, n=2; mucoepidermoid carcinoma, n=1; malignant lymphoma, n=10). The average time from symptom onset to diagnosis was 14.7 months (median=8 months; range=1-96 months). The analysis of patients revealed that lacrimal sac mass (22/25, 88.0%) was the most frequent symptom and a possible tumor marker. Most epithelial benign (n=3) and malignant epithelial (n=12) tumors were treated surgically (14/15, 93.3%). One malignant case was treated with heavy ion beam therapy. Eight patients were treated with postoperative (chemo)radiation therapy because of positive surgical margins (including one unanalyzed case). Local control was ultimately achieved in all but one case. The patient survived for 24 months with immune checkpoint inhibitors and subsequent chemotherapy for local and metastatic recurrence. We report our experience in the diagnosis and treatment of lacrimal sac tumors and analyze the clinical trends in cases involving these tumors. Postoperative radiotherapy and pharmacotherapy, including immune checkpoint inhibitors, may be useful for recurrent cases.