Pulmonary infections often complicate hematopoietic stem cell transplantation (HSCT) outcome. Uncommon aetiologies, like Mycobacterium tuberculosis, should be considered when the clinical conditions do not fully improve with standard antimicrobial therapy and microbiological evaluations are repeatedly negative for bacteria and fungi. We describe an interesting pediatric case of miliary lung tuberculosis after HSCT, which was successfully treated after administering the appropriate therapy.