<p><strong><em>Background:</em></strong><em> Dental and oral diseases which </em><em>a</em><em>re often found in children is dental caries. Streptococcus mutans </em><em>i</em><em>s the main cause of caries. Caries c</em><em>an</em><em> be prevented by using a topical application of fluoride. The Anchovy (Stolephorus insularis) contain</em><em>s</em><em> protein, vitamins (A, B₁, C), and minerals (Fe, Ca, K, F). Calcium fluoride (CaF₂) within the anchovy c</em><em>an</em><em> inhibit the occurrence of dental caries. <strong>Purpose</strong></em><strong><em>: </em></strong><em>The aim of this study was </em><em>to </em><em>determine the </em><em>antimicrobial </em><em> ability of anchovy extract (Stolephorus insularis) to Streptococcus mutans. <strong>Materials and</strong> <strong>Methods: </strong>This study was a laboratory experimental research </em><em>with</em><em>  post test only control group design. Diffusion method were applied with 2 controls: negative control used DMSO 1%, positive control used NaF solution, and 3 concentrations of anchovy extract (Stolephorus insularis) 3%, 6%, and 12%, each group were composed of 6 samples. </em><em>Antimicrobial</em><em> was assessed by measuring the diameter of the clear zone around the discs contained the anchovy extract (Stolephorus insularis). Data were analyzed by Kruskal-Wallis test followed by Mann-Whitney test.<strong> Result:</strong> The results from this study showed clear zone around the discs of the anchovy extract (Stolephorus insularis). The more concentration of the extract showed the more </em><em>antimirobial</em><em> zone diameter. The average zone of </em><em>antimicrobial</em><em> at  </em><em>the </em><em>concentration of  3% </em><em>were </em><em>7,11 mm, 6%</em><em> </em><em>9,5 mm, 12%</em><em> </em><em>10,78 mm, for the negative control DMSO 1% 6 mm and the positive control NaF solution 8,16 mm. The largest diameter of the clear zone was at concentration of 12% (P &lt; 0,05).</em><em> </em><strong><em>Conclusion: </em></strong><em>The<strong> </strong>anchovy extract (Stolephorus insularis) had an antimicrobial effect to the growth of Streptococcus mutans.</em><em></em></p>