Background: Rhodoccocus equi, Brucella abortus, and Pasteurella multocida are important veterinary bacterial pathogens that in recent years have been resisted to current antibiotics, and this problem threats the livestock industry. To control this resistant microorganisms, use of new antibacterial compounds, such as thiazole derivatives, in veterinary is necessary. OBJECTIVES: In this study, antibacterial effects of thiazole derivatives on Rhodoccocus equi, Brucella abortus, and Pasteurella multocida were evaluated. METHODS: Synthesized thiazole derivatives were prepared in DMSO, then the disk diffusion method was used to measure growth inhibition zone diameter and the broth microdilution method was applied to determine the minimum inhibitory concentration (MIC). RESULTS: Results showed that thiazole derivatives had no significant inhibitory effects on B. abrotus, while they had inhibitory effects on R. equi and P. multocida with inhibition zone 12.7±0.4 -30.1±0.2 mm and MICs 32- 256 μg/ml. CONCLUSIONS: Results of this study indicate that thiazole derivatives have considerable inhibitory effects on R. equi and P. multocida as veterinary bacterial pathogens.