Abstract: Gray mould, caused by Botrytis cinerea, is globally widespread and probably the most important disease of strawberry (Fragaria x ananassa Duchesne). It can cause significant pre- and post-harvest losses. Although application of synthetic fungicides is the most effective way to control the disease occurrence, biological agents, such as Bacillus spp. are becoming increasingly important, due to their environmentally friendly and consumer safety properties. The aim of this study was to evaluate the potential of Bacillus subtilis strain BS10 (cultivation liquid with 1.5 × 108 cfu/ml) to be used as a biocontrol agent against B. cinerea in strawberry. The trial was set in 2017 vegetation period at two localities in Serbia (Kisač and Bečej) in strawberry open field crops, according to EPPO method PP 1/16 (2). Three concentrations of B. subtilis strain BS10 (0.5, 1 and 2%) were tested and compared with standard fungicide boscalid + piraclostrobine, applied at a label rate. An untreated plot served as a control. In total, six treatments were applied, starting from the beginning of flowering. The effect of the tested products was assessed based on the intensity of mature fruit infection. According to the obtained results, B. subtilis BS10 strain, applied at concentration of 2%, was highly effective in the control of B. cinerea, with efficacy ranging from 79% (locality Kisač) to 85% (locality Bečej). In order to obtain a complete evaluation of the potential of B. subtilis BS10 strain in strawberry protection against B. cinerea, further investigation considering formulation improvements, adjustment of concentration and timing of application is desired.