In this study the effects of Salvia officinalis L. essential oil on the thickness of the gut mucus layer and quantity of neutral and acidic mucins in chickens were observed. Oneday-old chickens of Isa Brown breed were divided into five groups (n = 9) and fed 11 weeks as follows: control group (C): basal diet; experimental groups (E1 - E4) - same as C + sage essential oil (EO) in concentrations of 0.01%; 0.025%; 0.05% and 0.1%, respectively. The thickness of the mucus layer in the duodenum significantly increased in E3(0.05% sage EO) compared to E1 (0.01 % sage EO). In E3 (0.05% sage EO) the number of goblet cells containing acidic and neutral mucins was significantly decreased in the duodenum and jejunum and increased in the ileum compared to C. Feeding the diet supplemented with Se and 0.01% sage EO (E1) decreased plasma cholesterol level in comparison with E3(0.05 % sage EO). The addition of 0.05% (E3) and 0.1% sage EO (E4) to the diet caused a decrease in calcium plasma level compared to E2 (0.025 % sage EO). Plasma glucose level was significantly decreased in groups fed 0.05% (E3) and 0.025% sage EO (E2) compared with 0.01% sage (E1). The weight of internal organs was not affected by the diets. Our results suggest that effects of sage EO on the adherent mucus layer dynamics and mucin type distribution in the chicken intestine are dependent on sage EO dose and intestinal segment and there is still a need for further studies in order to obtain a plausible explanation.