The aim of the study was to determine the impact of triploidization on hematological and blood gas parameters in Siberian sturgeon, Acipenser baerii Brandt. The study material was comprised of juvenile Siberian sturgeon specimens with total body lengths of 22.3 ± 2.9 cm and mean body weights of 75.3 ± 40.7 g. Triploidization was confirmed to result in significant changes in the hematological profile of Siberian sturgeon. In comparison to the diploid group, the fish with higher levels of ploidy exhibited lower erythrocyte counts, increased hemoglobin concentration, and increased values of mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration. A significant decrease in the percentage share of lymphocytes and an increase in the percentage share of granulocytes in the peripheral blood were also observed, which indicate disturbances in the immune response (particularly in the adaptive immune system) and greater susceptibility to stress. Triploidization did not, however, cause significant differences in the blood gas profile.