This study was aimed at the comparison of the effects of dietary applications of sage essential oil (Salvia officinalis L.) on some digestive enzyme activities in the chyme of the jejunum, digestive characteristics, and selected bacterial microflora in the caecum. Seventy, one-day-old broiler chickens (Ross 308) were allocated into two equal groups for 42 days. The feed mixture of the experimental group was supplemented with the essential oil at the level of 2.306 g.kg−1. This supplementation was absent in the control feed mixture. The main volatile compounds were analysed: Eucalyptol 85, alpha-thujon 148, betathujon 72, camphor 149 and borneol 37 g.kg−1. The digestive enzyme activities in the chyme of the jejunum increased as follows: amylolytic on days 16 (P < 0.01) and 29 (P < 0.001) as well as cellulolytic on days 16 (P < 0.05), 29 (P < 0.001), and 42 (P < 0.01). The proteolytic activity decreased on day 16 (P < 0.01). The intake of the additive, increased the digestibility of crude fibre (P < 0.01) on days 16, 29 and 42. The apparent assimilable mass coefficient of crude protein, corrected for protein catabolism, was increased in the experimental group on days 29(P < 0.05) and 42 (P < 0.01). The counts of Escherichia coli in the caecum decreased (P < 0.05) on days 29 and 42. The supplementation of chickens with the sage essential oil increased the crude fibre digestibility, the amylolytic and cellulolytic activities in the chyme of the jejunum, and decreased the counts of E. coli in the caecum.