In the current study, an agar disc diffusion test was used to determine whether or not the thyme essential oil (TEO) had antibacterial properties. Using gas chromatography-mass spectrometry (GC-MS), the essential oil of thyme was analyzed. It was found that thyme oil contained a total of 47 different chemical components. Thymol, P-cymene, terpinene, linalool, and endo-borneol were the most abundant metabolites that were quantified. Thymol, also known as 2-isopropyl-5-methylphenol, is a significant component of the essential oil that is found in plants belonging to the Lamiaceae family. Three bacterial strains (Streptococcus agalactiae, Streptococcus iniae, and Streptococcus fecalis) that cause streptococcosis in tilapia were chosen for the purpose of invitro evaluation to the antimicrobial activity of TEO at different concentrations. Gentamycin served as the control positive. the results showed that the zone of inhibition for Streptococcus agalactiae was greatest at concentrations of 1:1 and 1:2. However, when compared to Gentamycin, the zone of inhibition for concentrations of 1:3 was not significant. Compared to Gentamycin, the inhibitory zone produced by Streptococcus iniae and Streptococcus fecalis was not significant. In overall, TEO showed efficacy in suppressing the growth of the three strains of Streptococcus, with the most successful outcomes shown in inhibiting the growth of Streptococcus agalactiae.