Rosmarinus officinalis is an edible evergreen shrub with fragrance native to the Mediterranean area. It is widely used for culinary and medicinal purpose around the world. In this study, the antimicrobial activity of ethanol extracts of R.officinalis on broad range of oral microbial species including streptococci, actinomyces, lactobacillus, candida and periodonto-pathogenic bacterial species was studied for possible usage of extracts of R. officinalisin dental care products for example mouth wash solutions and tooth pastes. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined by a microdilution method in culture medium. The MICs of ethanol extracts of R. officinalis for oral streptococci were between 31.25 and 250 µg/ml and MBCs were between 31.25 and 500 µg/ml. Actinomyces naeslundii and Actinomyces odontolyticus showed MICs of 31.25 and 15.62 µg/ml, respectively, and MBC of 62.5 µg/ml. The MICs were 15.62 and 7.81 µg/ml for Fusobacterium nucleatum and Porphyromonas gingivalis, respectively. The bactericidal activities of extracts of R. officinalis against susceptible bacterial species were dependent on concentration of extracts and incubation time.The treatment of bacteria with extract changed the cell surface texture of Streptococcus mutans and P. gingivalis. The data of our present study suggested that extracts of R. officinalis would be a useful compound for the development of antimicrobial agents against oral pathogens.