Objective: The aim of this study was to compare in vitro the antibacterial activity of an ethanol extract of Erythroxylum coca Lam (EEE) and Schinus molle L. (EES) at 50% and 75% versus Streptococcus mutans ATCC 25175. Materials and Methods: This was a prospective, comparative, longitudinal experimental study. The ethanol extract of coca and molle leaves was obtained by the vacuum filtration method at concentrations of 50% and 75% and was compared with a positive control (0.12% chlorhexidine). Streptococcus mutans strains were isolated in a culture medium (Mitis Salivarius Agar) ideal for the growth of bacterial colonies. The antibacterial activity of the ethanol extract was carried out following the Kirby-Bauer disk-diffusion method in Mueller-Hinton agar to measure bacterial sensitivity. A value of P 0.05 was considered statistically significant. Results: Evaluation of the antibacterial effect of EEE and EES at 24 and 48 h showed that a concentration of 75% for both groups had the highest antimicrobial activity against S. mutans (11.2 ± 0.7 mm; 11.6 ± 0.5 mm and 11.3 ± 0.7 mm; 11.8 ± 0.5 mm, respectively). So, the results have shown that the concentration of EEE and EES of 75% has a greater efficacy than the concentration of 50%, but both concentrations are not as effective as chlorhexidine. Conclusion: EEE and EES at concentrations of 50% and 75% present antibacterial activity against S. mutans ATCC 25175.