This study aimed at investigating changes in selected peripheral blood parameters in male polar foxes fed diets with different supplementation of inulin: 0.25% (group El), 0.5% (E2) and 1% (E3). The blood for analysis was sampled from the brachial vein. The study showed that adding 0.25 and 0.5% of inulin to fox feed resulted in a lower content of haemoglobin (Hb) as well as mean mass of Hb in red blood cells in the 0.5% inulin group. The total count of thrombocytes decreased significantly with a higher level of prebiotic, while the total number of white blood cells and the percentage of different leukocytes tested remained invariable. The lowest supplementation of inulin affected the partial pressure of carbon dioxide, however, the remaining acid-base parameters did not change. The present study provides the first preliminary information about the effect of dietary inulin on some haematological indices and acid-base parameters in adult polar foxes. The results may be helpful in practice to improve the health condition of farmed polar foxes.