Purpose of the Study: Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoid malignancy worldwide. Its incidence increases with age and about 40% of cases occur in patients over 70 years. Herein, we describe a case of a frail elderly patient with renal insufficiency and DLBCL treated with R-mini-CHOP. Case Report: A 77-year-old man on maintenance hemodialysis started experiencing persistent fatigue. He was diagnosed with a large mass on the left lobe of the lung. Biopsy demonstrated a DLBCL, CD20 positive. The patient was assigned clinical stage IIBX, with a high age-adjusted international prognosis index. A proper geriatric assessment revealed a frail patient. Thus, an adapted chemotherapy regimen was proposed which consisted of R-mini-CHOP every 21 days, with a reduction of 10% in the doses of doxorubicin and cyclophosphamide. During the treatment, the patient went through regular dialysis sessions, 3 times per week, with an extra session performed 12 h after each chemotherapy administration. The patient experienced no adverse events or grade 3/4 toxicities. After 6 cycles of R-mini-CHOP, the patient achieved unconfirmed complete remission, and consolidation radiotherapy was performed. At the last follow-up, he was still in unconfirmed complete remission, with a progression-free survival of 11.3 months. Conclusions: R-mini-CHOP represented a reasonable treatment option for this patient with renal failure. The oncogeriatric approach led to a successful management of this frail patient, highlighting that an adapted plan of care is a key issue to improve the outcomes of elderly cancer patients.