Mastitis is one of the most costly diseases in the dairy industry. The use of antibiotics in the treatment of mastitis Leads to bacterial resistance and health problems for consumers. This study aimed to determine the antibacterial properties of essential oil of Thymus vulgaris on the bacteria Staphylococcus aureus, Escherichia coli and Staphylococcus were agalactia. Antibacterial properties of the essential oils were analyzed by disc diffusion method. The MIC and MBC were determined. By different concentration oils (10, 30 and 50%) significant difference in inhibition zone size was observed between 10%, 30% and 50%. There are no significant differences between concentrations of 30% and 50%.