Background: Dental caries is one of the most prevalent infectious diseases, the main etiologic factor of which is Streptococcus mutans. The present study aimed to evaluate the effect of the leaf extract and gum of Pistacia atlantica on the growth inhibition of S.mutans in comparison to chlorhexidine (CHX). Methods: In the present in vitro study, the antibacterial effects of the extract and gum of this plant were evaluated in comparison to that of CHX. The microbial sensitivity was evaluated by determining the diameter of the growth inhibition zone. In addition, the turbidity test was used to determine the minimum inhibitory concentration (MIC) of the materials against S.mutans. Results: No growth inhibition zones for S.mutans were detected around the materials derived from P. atlantica, while a 24-mm growth inhibition halo formed around CHX. The MIC values for CHX and the leaf extract and gum of P. atlantica were 1.256, 1.8 and 1, respectively. Conclusion: In general, the present study showed that the antibacterial effect of CHX on S. mutans was higher than those of P. atlantica derivatives. In addition, the P. atlantica leaf extract exhibited higher antibacterial activity compared to its gum, which is used as chewing gum in some regions.