Infectious diseases are the leading cause of FUO. A case of prolonged fever with hepatic and pulmonary tuberculosis as a final diagnosis is herein presented. A 4-year-old, otherwise healthy boy presented with an axillary temperature of up to 39.5ºC for the previous 3 weeks. His medical history revealed an occasional increase in body temperature up to 38.5ºC for the last 6 months. Physical examination revealed coarse breath sounds on the basal lung area. Chest X-ray showed mediastinal lymphadenomegaly and computed tomography revealed paratracheal conglomerated lymph nodes and a groundglass appearance on the right lung. There were multiple contrast-enhanced, hypoechoic nodules with central necrosis in the liver parenchyma on abdominal magnetic resonance imaging. Open liver biopsy yielded chronic granulomatous inflammation compatible with pathological findings of tuberculosis infection. The culture specimen was positive for Mycobacterium tuberculosis. The patient improved rapidly after antituberculous therapy was initiated. Tuberculosis, especially in its disseminated form, poses a distinct diagnostic challenge in cases of prolonged fever with unproven etiology, and thus persistence should be exercised in disclosing the cause of such fevers.