In this study, the effects of thyme essential oil, added in different amounts to the diet of quails on some microbiological and physicochemical properties of breast meat were investigated. A total of 200 sixteen-days-old Japanese quails (Coturnix coturnix japonica) constituted the material of the study. Four groups were established, including a Control group and groups Thyme1, Thyme2 and Thyme3, which received a basal diet alone, a basal diet + 150 mg/kg thyme essential oil, a basal diet + 300 mg/kg thyme essential oil and a basal diet + 450 mg/kg thyme essential oil, respectively. Each group was randomly divided into 5 subgroups, comprised of 10 quails each. It was observed that neither thyme essential oil supplementation nor storage period had an effect on water activity (aw), pH and color parameters [L*(lightness), a*(redness), b*(yellowness)] of breast meat (P>0.05). Also, it was determined that thyme essential oil applications had a limited and variable effect on coliform, Lactobacillus spp, total psychrotrophic aerobic bacteria (TPAB) and Pseudomonas spp. (P<0.05). As a result, it was observed that thyme essential oil which added to the feed had a limited positive effects on quality and shelf life of breast meat.