This study aimed to investigate biochemical, histological, and genetic alterations in the skeletal muscles of rats subjected to varying temperature degrees within the first 6 hours postmortem. The study involved 35 mature male Sprague Dawley rats, divided into a control group of five rats with baseline measurements  “zero hour values", the remaining thirty rats allocated into two groups, one was kept in the refrigerator (4 ºC) and the other was kept at room temperature (22 ± 2 ºC). Rats from the two groups were categorized into three subgroups (n=5), with muscle samples dissected at 2, 4, and 6 hours (hrs) postmortem. Rats were euthanized through cervical dislocation, and muscle specimens were collected at time points of zero, 2, 4, and 6 hrs postmortem at both temperature conditions for the assessment of biochemical, histopathological, and genetic alterations. The results demonstrated that the concentration of lactate dehydrogenase (LDH), lactate, and creatine phosphokinase (CPK) increased in muscles that stayed at room temperature than those that remained at 4 ºC. In addition, glutathione peroxidase (GPX) activity increased, while the malondialdehyde (MDA) level decreased in muscles stored at 4°c compared to those maintained at room temperature.  Histological and histochemical analysis revealed a lack of cross striation, vacuolation of muscle fibers, and fragmentation after 4 and 6 hrs, with these changes being more pronounced at 22°C. The immunohistochemical analysis of caspase-3 immunoactivity indicated a significant decrease after 6 hrs at 22℃ group   compared with the zero-time group.