The development of increasing resistance to antibiotics such as colistin, problems arise in the treatment of bacterial infections and make it necessary to search new alternative methods. For this purpose, plant-based approaches are among the important research topics depending on their traditional uses. The aim of the present study was to investigate the antibacterial and antibiofilm activity of tea tree oil purchased from a local market against a variety of 66 colistin resistant Salmonella enterica serotypes isolated from poultry farm environmental samples. Content analysis of TTO was determined by gas chromatography/mass spectroscopy. The antibacterial activity was determined by broth microdilution method, and antibiofilm activity was examined by crystal violet method. As a result, terpinen-4-ol was found as major component of TTO with 35.9% ratio. The MIC values of TTO were differed between 6250-12500 µg/mL. 27 of 66 isolates formed biofilm and 25 of 27 isolates belonged to S. Infantis. The biofilm reduction of TTO at subinhibitory concentration were found between 52-84.4%. Current study should be supported by future studies to determine the effectiveness of TTO to be among the agents that can be used together with antimicrobials in the attenuation of microorganisms.