The aim of this study was to evaluate the antimicrobial effects of essential oils (EOs) isolated from Myrtus communis L. (myrtle) against Streptococcus mutants, Streptococcus sanguis, and Streptococcus salivarius through in vitro experiments. The EOs was isolated from myrtle leaves by the hydrodistillation method. The disc diffusion method was used to evaluate the zone of microbial growth inhibition by different concentrations of the EOs. The inhibition zone for all concentrations was measured in diameter (MM) after incubation at 37°for 18 hours. According to these measurements, the Minimal inhibitory concentration for each bacterium was reported. Tetracycline and erythromycin were used as positive control. The result showed that EOs of myrtle leaves had antimicrobial activity on disk-diffusions plates against all strains of Streptococcus, which were tested; however, S. mutants showed greater susceptibility than others. EOs of myrtle leaves could be recommended as a potential remedy for prevention the colonization of teeth by Streptococcus mutants and hinder the development of dental caries.