Objective:Different fluoride varnishes are used for the prevention of dental caries. The aim of this study was to compare the antimicrobial effect of different fluoride varnishes, containing xylitol and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), on Streptococcus mutans.Materials and Methods:In this in vitro study, the antibacterial effects of four varnishes, namely Polimo and V-varnish (containing xylitol), MI varnish (containing CPP-ACP), and Preventa, were evaluated against S. mutans. The disc diffusion method was used for testing the bacterial sensitivity. The data were analyzed using the Kruskal–Wallis and Mann–Whitney U-tests.Results:According to the results, Polimo showed the highest antibacterial effects, compared to the other three varnishes (P ≤ 0.05). Growth inhibition zones were not observed in V-varnish and Preventa. The mean diameter of inhibition zone around the MI varnish was significantly higher, compared to those of the V varnish and Preventa (P ≤ 0.05).Conclusion:As the findings indicated, the fluoride varnish containing xylitol and CPP-ACP could be more effective iAQ1n the prevention of dental caries.