Purpose: The aim of this study was to evaluate the antimicrobial effect of Extra virgin olive oil extract as mouthwash in the oral cavity of children against streptococcus mutans and Compare the efficiency between olive oil and the “gold standard" chlorhexidine. Materials and Methods: A total of 60 Egyptian children from both sex were included in this study. Children age ranging from 6 to 12 years old in a good physical condition. Children randomly were distributed into two Groups A and B, each includes of 30 children in each group. Group A(study group) : olive oil(Extra vigin): consisted of thirty children, each participant was instructed to rinse with 2ml of olive oil extract twice a day each rinse for about 1 minute for 3 weeks. Group B (Control group): chlorhexidine mouthwash (0.2%): consisted of thirty children, each participant was instructed to rinse with 2ml of chlorhexidine mouthwash (0.2%) twice a day each rinse for about 1 minute for 3 weeks. Results: There was a significant reduction in mean Streptococcus mutans count in the 2 groups after the study. Conclusion:olive oils can be used as valuable preventive agents in maintaining and improving oral health in low socioeconomic status population.