BACKGROUND AND AIM: In recent years, propolis has been introduced as one the most efficient agents against cariogenic bacteria. However, due to the lack of data on the propolis collected from Kandovan (Easthern Azarbaijan, Iran), this study was designed to investigate the effect of this type of propolis on Streptococcus mutans (S. mutans).METHODS: In this experimental study, the ethanolic extraction of propolis (EEP) was prepared with different concentrations (1%, 3%, 5%, and 10%) while the distilled water was incorporated as control. The antibacterial efficacy was tested via two standard methods including the agar disk diffusion and minimum inhibitory concentration (MIC) tests. Finally, the resulting data were analyzed using one-way analysis of variance (ANOVA) and Bonferroni post-hoc tests (a = 0.05).RESULTS: The obtained MIC was 2.5 mg/ml. However, in disk diffusion test, the 1% and 3% EEP solutions did not exhibit any zone of inhibition, however the 5% EEP showed very strong antibacterial effect (P < 0.001).CONCLUSION: The EEP extracted from Kandovan had significant antibacterial effect against S. mutans when prepared in 5% concentration. Therefore, this type of propolis could be considered as one of the most efficient propolis against S. mutans.