Introduction: Diffuse large B cell lymphoma (DLBCL) has an increasing incidence in elderly patients with poorer prognosis than in younger patients. Clinicians should clearly identify the characteristics and prognostic factors of elderly patients. We analyzed the outcome of elderly DLBCL patients, especially factors affecting survival in real-life clinical practice. Materials and Methods: The data of 330 DLBCL patients at our center were retrospectively evaluated by dividing three groups; younger than 65 years, between 65–79 years, and 80 years and older. We examined the factors affecting survival in DLBCL patients ≥ 65 years old. Results: The median age of the patients was 61 years (range 16–87). 192 (58.2 %) of our patients were younger than 65 years old, 112 (33.9 %) were between 65−79 years, and 26 (7.9 %) patients were 80 years old or older. The median follow-up was 15 (1–120) months. Median PFS was 38 months in the 65−79 years group, ten months in the ≥ 80 years group; meanwhile, median OS was 43 months in the 65−79 years group, 25 months in the ≥80 years group. The number of patients who relapsed within 12 months of the first-line treatment was 69 (35.9 %) in the <65 years group, it was 60 (53.6 %) in 65−79 years group, and 22 (84.6 %) in ≥80 years group (p < 0.001). The median OS was 9 (7.1–10.9) months in DLBCL patients older than 65 years old who relapsed within 12 months. Early relapse, failure to achieve CR after first-line chemotherapy, and high IPI score were associated with poor survival in patients ≥ 65 years old (p:0.001). Conclusion: Advancing age was a poor prognostic factor for survival of DLBCL. Relapsing within the first year, or failure to achieve complete remission were associated with poorer survival of the elderly DLBCL patients. R−CHOP is the standard treatment in DLBCL, and the best responses are obtained regardless of age. Due to difficulty in receiving standard treatments, novel treatment modalities are needed for better outcomes in elderly patients with DLBCL.