Estimation of the postmortem interval (PMI) is a very essential task for forensic experts especially in criminal cases. The PMI is the time passed since the death of an individual and refers to the stages of autolysis. This study aimed to estimate PMI from mRNA expression of Caspase-3 and IL-1β in the brain and adrenal gland of adult albino rats and the autolytic changes of these organs at time of death (0 hour), and then on 6, 12, 24, 48 hours postmortem (10 wistar male albino rats for each time). The results revealed a significant time-dependent elevation in the Caspase-3 mRNA expression levels of the brain and adrenal gland tissues, starting 6 h till 24 h postmortem then a significant reduction occurred at 48 h postmortem. On the other hand, the mRNA expression levels of IL-1β gene of the brain and adrenal gland tissues showed significant time-dependent reductions began at 6 h till 48 h postmortem. The results of the study concluded that the adrenal glands could be helpful for histopathological examination before 48 h at 20 °C and the brain tissue especially hippocampus could be helpful for histopathological examination before 12 h at 20 °C.