The aim of the study was to determine whether silver nanoparticles (Ag-NPs) administered per os to chickens as a hydrocolloid at a dose of 2.87 or 12.25 mg per bird per whole experiment (D1 and D2, respectively) will affect the accumulation of this element in tissues, immune and antioxidant responses, and how the increasing of the Ag-NPs size from 5 nm to 25 or 40 nm (S-5, S-25 and S-40, respectively) will influence these processes. The experiment was carried out on 280 chickens assigned to 7 experimental groups. The control group did not receive Ag-NPs. Other chickens received a hydrocolloid of Ag-NPs at a concentration of 5 mg · l^–1 in the drinking water in 1 cycle × 7 days (days 8–14 of life) for D1 and in 2 cycles × 7 days (days 8–14 and 36–42 of life) for D2. Neither Ag-NPs addition influences performance parameters of birds. All sizes of Ag-NPs were accumulated in the intestine and liver with the higher dose the higher accumulation relation. The villus height to crypt depth ratio in jejunum was decreased by Ag-NPs administration. All doses and sizes of Ag-NPs stimulated the immune system (except S-40_(D1) treatment) and intensified oxidation stress in relation to the control group. However, the changes observed in the immunological indices do not allow to draw clear conclusions about the occurrence of inflammation state in the organism of chickens receiving Ag-NPs. Concluding, it has been demonstrated that oral administration of Ag-NPs to chickens influences the morphology of the gastrointestinal tract and the parameters of immune and redox status. This effect varies depending on the dose and size of used Ag-NPs, so there is still a need for further investigation in order to assess the suitability of Ag-NPs in poultry nutrition.