Abstract Background No comprehensive analysis has evaluated the appropriate relative dose intensity (RDI) of R-CHOP treatment in elderly patients. This study aimed to clarify the relationships between the RDI of R-CHOP treatment and susceptibility of febrile neutropenia (FN) using a national inpatient database in Japan. Methods We identified patients with newly diagnosed diffuse large B-cell lymphoma (DLBCL) who received the first R-CHOP treatment between July 2007 and March 2017 from the Japanese Diagnosis Procedure Combination Database. RDI was calculated according to a comparison between the actual cyclophosphamide dose and the 100%-dose cyclophosphamide. Multivariable logistic regression analysis was performed to identify factors associated with the incidence of febrile neutropenia (FN). Results FN occurred in 1,465 of the 18,095 (8.1%) patients, at a median of 10 days (IQR, 8-12) from the initiation of the chemotherapy. Compared with the >100% RDI group, multivariate analyses showed that each low-RDI group (80%≤RDI Conclusions Our study suggests that low-RDI R-CHOP treatment decreases the susceptibility of FN in patients who are over 70 years of age.