There were many conflicting results about the significance of postmortem thyroglobulin (Tg) level as a biomarker in forensic diagnosis. This work aimed to assess the relation between postmortem blood Tg level and the cause of death. Sixty cadavers received at Cairo Department of Forensic Medicine (Zenhum Morgue), Egypt, were classified into two groups; 1st group included 30 cadavers died by different types of asphyxia, and 2nd group included 30 cadavers died by causes other than asphyxia. In all cases, right heart blood (RHB) and left heart blood (LHB) Tg levels were measured using chemiluminescence immunometric assay and thyroid tissues were histopathlogically examined. Thyroglobulin level was high in 76.6% of 1st group cases and in 83.3% of 2nd group cases. In fatal traumatic brain injury cases, there was a significant positive correlation between Tg level and survival period. The mean value of RHB Tg levels was higher than that of LHB Tg levels in both studied groups while Tg was high in all cases with skin discoloration as a sign of putrefaction regardless of the cause of death. In conclusion, thyroglobulin level is unreliable as a diagnostic tool for cause of death because it may be affected by postmortem changes.