It is generally believed that trauma from child abuse or bone fragility from diseases such as osteogenesis imperfecta accounts for most cases of multiple rib fractures. We report an infant with unexplained fractures from the right 3rd rib through to the 8th rib who had undergone resection of a large cervical tumor and had been admitted to a neonatal intensive care unit. Neither trauma nor bone fragility disease was found in the patient during the detailed investigation conducted by the Malpractice Investigative Committee.