Plants contain a wide variety of active compounds that exhibit antimicrobial activity. Even though the antimicrobial activity of plant extracts is well documented, the exact mechanism of action is not fully understood. The antimicrobial effectiveness of plant extracts depends on effective methods of extraction. Direct extract or juice could provide an effective method to obtain maximized levels of antimicrobial activity. In addition, due to the fairly recent surge in the antibiotic resistance of pathogenic microorganisms and increasing consumer concerns regarding the negative health impact of synthetic preservatives, there has been a dramatic increase in the application of natural antimicrobials of plant origin. This chapter summarizes current research on the various antimicrobial mechanisms of action of plant extracts, development of extraction techniques, and how the extract affects Gram-positive and Gram-negative bacteria. Finally, the chapter outlines potential applications of plant extracts as antimicrobials in food systems.