Introduction Fire death investigations attempt to determine whether a subject was alive or dead before the fire started. Therefore, it is essential to assess if the bone damage is traumatic or the result of exposure to heat. This observational study aims to expose the specific CT semiology of thermal bone lesions to allow the forensic radiologist to identify and distinguish them from traumatic lesions that would have preceded death. Materials and methods We retrospectively reviewed the CT findings of 25 bodies with thermal bone lesions for which a postmortem computed tomography (PMCT) was performed prior to an autopsy. Imaging findings were correlated to the autopsy data to identify the specific features of thermal bone lesions. Results Specific signs of thermal injuries to bone were identified on PMCT on all deceased cases. Thermal damages predominated in areas directly exposed to flames (rib cage, distal extremities) with less soft tissue coverage (“soft tissue shielding”). The mottled appearance of bone marrow was a constant sign of burned bones. Heat fractures such as trans-diploic fractures of flat bones and beveled (“flute-mouthpiece”) fractures of extremities seemed specifically related to thermal mechanism. In addition, we provided a better description of superficial cortical fissures of flat bones (“ancient Chinese porcelain”) and observed a “stair step” fracture of a long bone until now undescribed in radiological literature. Conclusion Thermal bone lesions have specific CT findings, different on several points from traumatic injuries. Their knowledge is essential for radiologists and forensic physicians to provide an accurate report of injury and conclusions.