Background: Herbs are being widely explored to discover alternatives to synthetic antibacterial agents.Small Cardamom often referred to as queen of spices because of its very pleasant aroma and taste, have a history as old as human race. Most people use cardamom as a spice and are largely unaware of its numerous health benefits. The purpose of this study was to evaluate the effect of different concentrations of water and alcoholic cardamom extracts on sensitivities, growth, and adherence of Mutans streptococci in vitro. Materials and Methods: In this study, saliva was collected from ten volunteers (College students 18-22 years). Agar well technique was used to study the sensitivities of Mutans streptococci to different concentrations of small cardamom extracts and other control agents, also the effects of small cardamom extracts on viable counts, adherence of Mutans streptococci were studied Results: According to agar well diffusion methods, both cardamom extracts were effective in inhibition of Mutans streptococci, but still weaker than chlorhexidine gluconate 0.2%. Alcoholic extracts showed higher zone of inhibition compared to the same concentration of water with high significance differences (P<0.01). The effects of 10%, 15%, and 20% of both water and alcohol extracts of small cardamom were tested on the viability counts of Mutans streptococci in vitro. Highly significant reduction in the counts of bacteria was reported of both cardamom extracts and CHX in comparison to control without agents after 24 hr. Both cardamom extracts less effective than CHX. All the concentration of water and alcohol cardamom mouth washes tested was not effective in prevention the adherence of bacteria on teeth surface in vitro, while CHX was effective in prevention the adherence of bacteria. Conclusion: Cardamom extracts were effective against Mutans streptococci, but still less than CHX.