Tuberculous meningoencephalitis is a rare disease associated with high morbidity and mortality. We report a patient with hairy cell leukemia in complete remission who, after a single cycle of chemotherapy with cladribine, presented fever and neurological deficits. Laboratory diagnosis of tuberculous meningoencephalitis was made by polymerase chain reaction testing for Mycobacterium tuberculosis in cerebrospinal fluid. Despite the prompt institution of antitubercular-therapy, patient's general condition did not improve and he died. Mycobacterial infection should be considered in patients with intra-cranial lesions, affected by hematological malignancies and persistent immunosuppression.