In this study, the essential oil (EO) of Pistacia atlantica subsp. kurdica was added at the rate of 10 g/kg of daily diet of rainbow trout and its effect on gut microbiota (Enterobacteriaceae, Lactobacillus spp., total count), growth performance and antioxidant status of rainbow trout fillet was investigated. Sixty apparently healthy rainbow trout with an approximate weight of 150 g ±3.5 were randomly divided into treatment and control groups. Physical and chemical conditions of water were adjusted to optimal for fish farming and sampling was done after 3 months. The results showed that feed conversion ratio in the control group was significantly (p < /em><0.05) lower than that in the treatment group. The total number of intestinal bacteria was significantly reduced in the treatment group (p < /em><0.05), but the amount of this reduction in Lactobacillus spp. was lower than other bacteria. The oxidative status of fish fillet in the treatment group was not significantly different from that in the control group (p < /em>>0.05) after 1 and 7 days cold storage (3°C). According to the obtained results, the EO of Pistacia atlantica kurdica at this dose is not advised for increasing the shelf life of meat and growth performance of fish.