Objective: To determine the in vitro antibacterial effect of different concentrations of the ethanol extract of Plantago major (plantain) on Porphyromonas gingivalis and Fusobacterium nucleatum. Material and Methods: Bacterial susceptibility tests were used in conjunction with the agar diffusion test and the minimum inhibitory concentration (MIC) test using the broth macrodilution technique. Results: Different concentrations of ethanol extract (25%, 50%, 75% and 100%) dissolved in 70% ethanol were used, with a positive control (0.12% chlorhexidine + 0.05% cetyl-pyridinium chloride) and a negative control (70% alcohol). The extracts at 75% and 100% showed inhibition halos against both strains studied. With 0.12% chlorhexidine + 0.05% cetyl-pyridinium chloride, inhibition halos averaged 14.9 mm, in contrast to 70° alcohol, where no bacterial inhibition was observed. The MIC was 50% for both species. Conclusion: The ethanol extract of Plantago major presents an in vitro antibacterial effect on Porphyromonas gingivalis, they may have potential applications in food and pharmaceutical products.