The impact of pretreatment nutritional status on the treatment outcome of non-Hodgkin lymphoma has never been explored. Among the 953 patients who were registered in a prospective cohort at Samsung Medical Center., we analyzed 262 patients who had been treated with Ruximab-cyclophosphamide, doxorubicin, vincristine, and prednisone for newly diagnosed diffuse large B-cell lymphoma (DLBCL) and for whom data were available regarding pretreatment nutritional status. Nutritional status at diagnosis was assessed by triceps skin fold (TSF), mid-arm muscle circumference (MAMC), body mass index (BMI), serum albumin, prealbumin, and transferrin. For patients aged 60 yr and older, poor performance and higher tumor burden were associated with malnourishment represented by albumin <3.5 g/dL, prealbumin < 17 g/dL, and transferrin <170 mg/L. Lower BMI (<20), serum albumin, prealbumin, and transferrin were identified as risk factors for febrile neutropenia in univariate analysis, but not in multivariate analysis. In the univariate analysis for OS, all nutritional parameters except MAMC showed a significant association with survival. However, BMI was the only parameter that was independently prognostic for OS in the multivariate analysis (P = 0.031; hazards ratio = 3.32). Nutritional insufficiency encountered in DLBCL patients might influence the occurrence of treatment-related toxicity and poor survival outcome of patients.