The effect of dietary supplementation of vitamins A and E on total and differential leukocyte count as well as morphometric parameters of lymphocytes in peripheral blood of farmed dark-brown American mink (Neovison vison, Mustelidae, Carnivora) was examined. The mink were characterized by a relatively high number of leukocytes in blood with predominance of neutrophils and a lower content of lymphocytes. The parameters of lymphocytes (surface area and nuclei area) in control and experimental animals were determined by computer morphometry. Lymphocytes in mink peripheral blood were shown to vary in both cell surface area and in nuclei surface area. Supplementation with vitamins A and E for 14 days had no significant effect on the number of leukocytes and differential leukocyte count, but changed the morphometric parameters of lymphocytes. Both vitamins caused an increase in the surface area of the cells, cytoplasm dimensions, and vitamin E in a dose of 4 mg / animal promoted the nuclei surface area. The increase in the average size of lymphocytes occurred due to a decrease in the proportion of the smallest cells and an increase in the number of medium and large cells. This dependency was the most explicit in the groups receiving vitamin E. It was concluded that in mink the immunomodulatory effects of vitamins A and E led to a change in the parameters of lymphocytes, and, possibly, their morphofunctional state.