We report a case of pyrexia of unknown origin presenting with lactic acidosis and hypoglycaemia. He further developed Guillain–Barre syndrome (GBS) and Hemophagocytic lymphohistiocytosis (HLH). The bone marrow biopsy ultimately reported Diffuse large B cell lymphoma (DLBCL). A 74-year-old gentleman visited the hospital in January 2024 with a fever since 2 weeks. He further developed hypoglycemic episodes and lower limb followed by upper limb weakness. On physical examination, he was febrile, tachypnoec with hepatomegaly and bilateral lower limb weakness with grade 3 power proximally and extensor plantar reflexes. Peripheral smear showed a leucoerythroblastic picture and 3% atypical lymphoid cells. Procalcitonin, lactate dehydrogenase and Ferritin were markedly elevated, suggestive of HLH. The bone marrow biopsy ultimately revealed DLBCL. He was diagnosed with GBS, Warburg phenomenon and HLH secondary to DLBCL. Intravenous steroids were started for secondary HLH and after he became hemodynamically stable was initiated on chemotherapy with Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, Prednisolone (R-CHOP) regimen. After four cycles of R mini-CHOP, positron emission tomography–computed tomography showed a good response. Further two cycles of R mini-CHOP was given with methotrexate for central nervous system prophylaxis. This case portrays an atypical presentation of DLBCL with Warburg syndrome, GBS and HLH. Despite the adverse clinical course, the patient responded favourably to chemotherapy.