The resistance of microorganisms to antibiotics raises problems that have become one of the major concerns of human society and the health care system (1). With the emergence of antibiotic-resistant, the efficacy of existing drugs has decreased and this has increasingly enhanced the failure of antimicrobial therapies (2). Besides, the widespread use of industrial-origin drugs as well as improper use of these drugs can cause many side effects, sometimes resulting in more serious toxic effects than the disease itself (3). One way to prevent the emergence of antibiotic resistance is to use compounds that work similar to antimicrobial drugs but differ from existing industrial sources (4, 5). In fact, due to the increasing incidence of antibiotic resistance, there is a pressing need for new antibacterial drugs, and of the potential sources, such as plants (6). The use of medicinal herbs has been one of the earliest human achievements to treat most diseases in different countries, because the plants make compounds that are related to the antimicrobial properties, including alkaloids, flavonoids, isoflavonoids, tannins, glycosides, and phenolic compounds. In other words, secondary metabolites in plants have antimicrobial properties (7). Mentha includes more than 25 species, but the most common species used is Mentha piperita Lamiaceae (Peppermint). It is one of the most popular aromatic plants, which have traditionally been used in folk medicine. Peppermint is a combination of blue mint and ornamental or spicy mint (8). It has dark green and fragrant leaves and grows 60 to 90 cm. Peppermint is a perennial herbaceous plant whose leaves, are elliptic, transverse, serrate, slightly lanceolate, 4–7cm long and 2–3 cm wide. Peppermint has high menthol content and its oil also contains menthone and carboxyl esters. For this reason, it seems that it can have antimicrobial properties (9). Today, in different countries of the world, more than one thousand tons of oils are produced from this plant, which shows its importance in different parts of the world. Much research has been done on the medicinal properties of peppermint (10). Hence, the objective of this study was to assess the antimicrobial properties of Mentha piperita Lamiaceae on standard bacteria, including S. aureus, B. cereus, E. coli and P. aeruginosa in vitro.