Background: Eimeriosis in calves, often treated with harsh chemicals, leads to significant health and economic burdens. This study explores natural coniferous-phytogenic feed additives as an innovative solution, focusing on their efficacy against Eimeria bovis and Eimeria ellipsoidalis, two common eimeriosis pathogens in calves.Methods: The authors conducted experiments to analyze the therapeutic and preventive effectiveness of the use of a coniferous-phytogenic immunomodulator in the diet of calves from 5-7 days of age and a coniferous and salicylic acid feed additive from 28-30 days of age in case of eimeriosis infestation at a dose of 5.0, 10.0, and 15.0 ml, once a day, in courses of 2 weeks without intervals with a small amount of warm water.Results: The extensivity of the coniferous and salicylic acid feed additive against the eimeriosis infestation in calves caused by E. bovis showed maximum result. Both preparations were willingly consumed by calves and eliminated the signs of diarrheal dyspeptic syndrome and gastroenteritis. The inclusion of coniferous-phytogenic feed additives in the calves' diet from 5-7 days of age once a day, in courses of 2 weeks without intervals, contributed to 100% effectiveness against E. bovis and E. ellipsoidalis.Conclusion: The study concludes that coniferous-phytogenic feed additives are highly effective in treating and preventing eimeriosis in calves, showing 100% effectiveness against the targeted pathogens. These additives also contribute to the overall health and well-being of the animals by alleviating related symptoms.Keywords: Calves; Calf Pen; Eimeriosis; Coniferous-Phytogenic Feed Additives; Efficiency