Bone tuberculosis may mimic malignant tumor. We here report the case of a 4-year old child with bone tuberculosis mimicking femoral osteosarcoma. The diagnosis was rectified thanks to anatomo-pathologic examination. This case study underlines the importance of knowing the clinical and radiological aspects of bone tuberculosis which can mimic malignant tumor. In order to avoid any delay in diagnosis, surgeons, pediatricians and radiologists should know that tuberculosis can mimic many pathologies, both clinically and radiologically.