The available literature lacks information on the effect of Zakarpacki zeolite (clinoptilolite) on the immune system of poultry. Therefore, the aim of this study was to determine the effect of this zeolite on selected indicators of the immune response in poultry by evaluating the expression of cluster of differentiation (CD) surface molecules on T and B lymphocytes and the concentration of IL-2 and IL-10 in the blood. Ninety one-day-old Ross 308 broiler chicks were used in the study. The birds were divided into 3 groups of 30 each. The same basic diet was used in all groups, but groups II and III received a feed additive in the form of 2% and 3% zeolite. Blood samples were collected from all birds on the 40th day of observations. Weight gain in the birds in both experimental groups was significantly higher, and no clinical symptoms of disease were observed. The percentage of CD4+CD25+ T and B lymphocytes was higher in both groups receiving zeolite, but the percentage of CD8+CD25+ T lymphocytes was higher only in the group receiving 3% zeolite. There were no differences between the groups in the percentage of cells with CD3+ and MHC Class II expression. Higher serum concentrations of IL-2 and IL-10 were noted only in group III. The use of zeolites enhances antigen presentation and leads to increased Th1 and Th2 response. Excessive supply of zeolite in the feed leads to a local inflammatory response, which may cause damage to the intestinal barrier.