Since the introduction of rituximab (R), the prognosis for diffuse large B-cell lymphoma (DLBCL) has markedly improved. We evaluated the prognostic significance of serum soluble CD27 (sCD27) in 143 patients with DLBCL treated with cyclophosphamide, doxorubicin, vincristine and prednisolone plus rituximab (R-CHOP). Five-year overall survival rates for patients with sCD27≥213 U/mL or <213 U/mL were 38.7% and 76.8%, respectively (p =0.0005). Multivariate analysis revealed that serum sCD27 was significantly correlated with OS (p =0.047). Immunohistochemical staining for CD27 in lymphoma tissues revealed positive lymphoma cells in 22 cases (18.5%) and positive microenvironment T-cells in 62 cases (52.1%) and was negative in the remaining patients. In these three subgroups, median sCD27 levels were 336 U/mL, 242.6 U/mL and 109.9 U/mL, respectively (p =0.004). Thus, serum sCD27 level is associated with CD27 expression on lymphoma cells, and may be a powerful prognostic factor for DLBCL.