The objective of the research was to determine the chemical compositions and antibacterial and antifungal activity of essential oils from 4 medicinal plants consist of Mentha piperita, Mentha spicata, Anethum graveolens and Foeniculum vulgare. Antibacterial and antifungal activity of these oils and their components were assayed against a variety of human pathogenic bacteria. Main components in Mentha piperita oil were menthol, limonene, 1,8-cineole, sabinene, menthyl acetate and menthone, in Mentha spicata oil carvone, menthol, limonene and menthone, in Anethum graveolens leaves oil α-phellandrene, Dill ether and β-phellandrene and in Foeniculum vulgare oil terpin-4-ol, t-anethole, fenchone and estragole. Present results showed that oils extracted from leaves of Anethum graveolens and Foeniculum vulgare plants did not show antibacterial or antifungal activities. Mentha piperita showed strong antibacterial and antifungal activities, however, lower than Mentha spicata. Carvone possessed the highest antibacterial and antifungal activity among the tested components. Essential oils of Mentha species possess great antibacterial and antifungal potential and could be used as natural preservatives and fungicides.