BACKGROUND Brucellosis is a contagious bacterial disease caused by Brucella species, which is a leading zoonotic disease worldwide. Most patients with brucellosis have a clear infection source; however, our case had a rare presentation of secondary haemophagocytic lymphohistiocytosis without any epidemiological history. CASE SUMMARY A 50-year-old man was admitted to our hospital with a fever of unknown origin. After laboratory examinations, such as blood culture and bone marrow biopsy, the patient was diagnosed with brucellosis and secondary haemophagocytic lymphohistiocytosis. After antibiotic therapy, the patient was afebrile, and his haemogram recovered to normal, after which he was discharged. CONCLUSION Brucellosis cannot be excluded in patients with clinically unexplained fever, even in those without epidemiologic history.