The aim of the work was to determine the effect of drugs on the morphological parameters of the blood of calves during the mixed course of cryptosporidiosis and eimeriosis. Three groups of calves (n = 7) spontaneously infected with cryptosporidia and eimeria were formed. The treatment with brovitacoccid (group I) and the drug “Amprolev-plus” (group II) was carried out and the change in morphological parameters of the blood was determined before the use of drugs and on the 3rd, 7th, 14th and 21st days. In the spontaneous mixed course of cryptosporidiosis and eimeriosis of calves, the efficacy of brovitacoccid for cryptosporidiosis was 85.7%, for eimeriosis — 100%, while the efficacy of the drug “Amprolev-plus” for cryptosporidiosis was 100%, and for eimeriosis — 85.7%. In the mixed course of cryptosporidiosis and eimeriosis of calves, the restoration of morphological parameters of blood after the use of the drug “Amprolev-plus” was recorded on the 14th day, and brovitacoccid — on the 21st day. The proposed drugs restore the content of erythrocytes to the level of 6.91 ± 0.52 T/l and 6.86 ± 0.55 T/l and hemoglobin 115.85 ± 1.22 g/l and 116.22 ± 0.24 g/l. The number of leukocytes decreased by 28.9% and 35.7% compared to their number before treatment, lymphocytes — by 10.5% and 9.0%, monocytes — 10.5% and 8.8%. A positive correlation between the content of leukocytes and the absolute number of lymphocytes indicates the activation of the cellular immune system