A 33-year-old man was admitted in hospital due to fever, generalized lymphadenopathy, and hepatosplenomegaly. He had a history of anti-tuberculosis treatment in the previous 3 years. Despite normal chest radiograph, a sputum sample was smear-positive for acid-fast bacilli, and polymerase chain reaction was positive for Mycobacterium tuberculosis complex. Drug susceptibility test revealed resistance to isoniazid and rifampin. Evaluation of the patient's immune system revealed IL-12Rβ1 deficiency. The patient died of disseminated tuberculosis (TB), despite appropriate antibiotic treatment. This is the first IL-12 receptor-deficient patient presenting with disseminated TB in adulthood, without any previous relevant medical history. This diagnosis should be considered in selected adult patients with unexplained, overwhelming TB. IL-12Rβ1 deficiency is a genetic etiology of severe TB in adults and should be considered in adult patients with disseminated TB.