A 76-year-old woman with a past history of diabetes mellitus and Hashimoto's disease, in regard to her personal history, she did not smoke or drink alcohol. In March, year X-1, she became aware of cervical lymphadenopathy. Based on the findings of lymph node biopsy, she was diagnosed as having diffuse large B-cell lymphoma(DLBCL). An upper gastrointestinal endoscopy(U-GIE)revealed white granular prominences in the gastric fornix, and biopsy of these lesions revealed the diagnosis of Russell body gastritis(RBG). Neither lymphoma infiltration nor other malignant findings were found. Diagnostic tests for Helicobacter pylori were negative. The clinical stage of the DLBCL was determined as stage ⅢA, and the International Prognostic Index was"high intermediate". She received 6 cycles of R-CHOP therapy, with concomitant use of a proton pump inhibitor. Complete remission was confirmed in November, year X-1. An U-GIE performed again no longer showed the white granular prominences in the gastric fornix. The present report is the first of DLBCL complicated by RBG; our findings suggested that the two diseases were associated with each other.