The objective of the present study was to examine the effects of hydrocolloidal silver nanoparticles (Ag-nano) on microbial profile of caecum and morphology of enterocytes in duodenum of Japanese quail, as a model animal for poultry. Quails (Coturnix coturnix japonica) (10 d old) were randomly divided into four groups (15 quails each) and located into four cages for 12 days. Quails were fed with granulated diets given ad libitum and had free access to drinking water. Ag-nano were added to drinking water at concentrations of 0, 5, 15 and 25 mg/kg. At the end of the experiment, the animals were killed and samples of duodenum and caeca microflora were collected. This initial investigation demonstrated that silver nanoparticles did not influence emphatically microflora of quail caecum; however, water containing 25 mg/kg of Ag-nano significantly increased the population of lactic acid bacteria. Furthermore, Ag-nano did not show any damaging properties on enterocytes of duodenal villi.