Background: Allium vegetables, particularly garlic (Allium sativm) have been used for centuries to combat infectious diseases. It exhibits a broad antibiotic spectrum against many types of bacteria, and can be used for formulation of newer broad spectrum antibacterial substances.Objective: This study aimed to explore the antimicrobial activity of aqueous garlic extract on different types of bacteria which cause mouth sore and dental caries.Methods: The study was carried out in College of Medicine / University of Diyala. A total of 200 teeth swabs were collected from students of the college. The isolated bacteria were identified according to standard bacteriological methods and their susceptibility to different antibiotics was tested according to Kirby-Bauer method. Antimicrobial activity of different concentration of aqueous garlic extract was measured by MBC (Minimal Bactericidal Concentration) according to agar-dilution method.The results: Our study revealed that 187 (93.5%) were Streptococcus mutans (S.. mutans), and 144 (72%) were Staphylococcus aureus (S. aureus). The aqueous garlic extract was effective as antibacterial agent against S. aureus and S. mutans which were resistant to different antimicrobial agents. The averages of MBCs of extract against S. aureus and S. mutans were 2 mg/mL and 4 mg/mL respectively.Conclusion: Garlic extract has antibacterial activity in low concentration on S. aureus and S.mutans. Garlic extract is safe and inexpensive remedy that can be used as a better alternative especially in developing countries.