The results of experimental studies of changes in blood hematological parameters of arctic foxes (Vulpes lagopus (Linnaeus, 1758)) occurring on the first 24 hours after death of animals are presented. In vivo blood samples were taken from 7 months arctic foxes male (veil color) (n=35), and then postmortem blood samples were taken from the carcasses of the animals 1, 3, 6, 12 and 24 hours after death. In each blood sample, the total number of erythrocytes, hemoglobin concentration, hematocrit, average volume of erythrocytes, average content and concentration of hemoglobin in an erythrocyte, relative width of distribution of erythrocytes by volume, average platelet volume, relative width of distribution of platelets by volume, thrombocrit, total number of platelets, the total number of leukocytes, the leukocyte formula, as well as the parameters of erythrocytes (area, perimeter, diameter, thickness, sphericity index). The study showed that the morphometric parameters of the blood obtained from a living animal and its corpse in the first 3 hours after death are identical and do not lose their significance for diagnosing the physiological state of the animal, identifying pathologies, and establishing the influence of environmental factorsIn post-mortal blood, 6 hours after death, the number of segmented neutrophils significantly decreases (p<0.05) and due to this, there is a shift in the leukocyte formula towards lymphocytes. The number of rod-shaped neutrophils and eosinophils does not change. After 6 hours after death, single destroyed neutrophils occur, and after 12 hours their significant (p < 0.05) decrease occurs. The identity of the parameters of the erythrocytes of the intravital and postmortal blood of Arctic foxes in the first 3 hours after death was established. After 6 hours, significant (p<0.05) differences were noted between the lifetime and postmortem samples in the area, perimeter, diameter and sphericity index of the erythrocyte. When microscopy of erythrocytes from cadaveric blood, it is more difficult to find visual fields suitable for measurement. It seems necessary to examine a larger number of visual fields to obtain reliable results. The data obtained indicate that peripheral post-mortem blood can be used both for studying intravital parameters and for assessing the post-mortem interval in mammals.