© The Author(s) 2020.Introduction: Hemophagocytic lymphohistiocytosis (HLH) is an aggressive and life-threatening syndrome of excessive immune activation. Herein, we aimed to report a diffuse large B-cell lymphoma (DLBCL) case that was presented as HLH. Case report: A 32-year-old man presented to a hospital with complaints of vomiting, nausea and diarrhea in October 2019. Fever and hepatosplenomegaly was detected in physical investigation. Bone marrow aspiration investigation revealed the hemaphagocytosis. HLH-2004 protocol was started for hemophagocytosis. Whole body magnetic resonance imaging (MR) revealed no lymphadenopathy. Bone marrow biopsy revealed high-grade B-cell lymphoma, favoring DLBCL. There were no pathologic cells in lumber puncture investigation. Management and outcome: He was diagnosed with secondary hemaphagocytic syndrome due to DLBCL, and chemotherapy was switched to rituximab, etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin (R-EPOCH) regimen. After three cycles of R-EPOCH chemotherapy regimen, complete remission was confirmed with positron emission tomography-computerised tomography (PET-CT) scan. Discussion: Our patients’ findings are suitable for six out of eight criteria of hemaphagocytic syndrome. The H-score of our patient was more than 250, reflecting the >99% probability of HLH syndrome. Compatible with literature knowledge, our patient had responded very well to etoposide-containing regimens. In our patient, no lymphadenopathy was detected by physical examination or MR scan, and the diagnosis of DLBCL was only made by the result of bone marrow investigation. In conclusion, herein, we have reported a DLBCL case that had presented with HLH, and clinicians should be aware that B-cell lymphomas may be the underlying cause of HLH.