Introduction:Streptococcus sanguinis is a primary colonizer in oral biofilm formation. This species is often impli-cated in infective endocarditis. Besides its important role in systemic disease and antimicrobial resistance, methods to control oral biofilm formation need to be developed. Garlic (Allium sativum) has shown antimicrobial activities against many pathogen species. The purpose of this study was to analyze the ability and optimal concentration of garlic extract required to inhibit bacterial adherence to hydroxyapatite (HA) discs as a model of the tooth surface. Methods: Saliva coated HA discs were incubated with various concentrations of extract then stimulated with S. sanguinis ATCC 10556 suspension to analyze the ability of garlic extract and the optimal concentration required to inhibit bacterial adherence. A motility assay was performed using inoculated bacteria treated in a Motility Indole Ornithin (MIO) medium. Results: It was shown that garlic extract could inhibit bacterial adherence to HA discs. Moreover, there was motility inhibition of S. sanguinis-treated as the extract concentration increased in MIO medi-um. Statistical analysis using One-way Anova demonstrated a significant difference in optical density (OD) value between groups (p<0.05). Conclusion: Garlic extract has the ability to inhibit adherence of S. sanguinis to HA discs, through its inhibitory effect on bacterial motility, with the optimal concentration being 250 μg/ml.