Introduction: Pelargonium peltatum (L.) L'Her (ivy geranium) is widely used in natural medicine for the treatment of oral disease, but its pharmacological properties, antibacterial activity and phytoconstituent composition are still unknown. Objective: carry out a comparative study of the in vitro antibacterial activity of the aqueous extract obtained from leaves of Pelargonium peltatum (L.) L'Her (ivy geranium) against Streptococcus mutans, Streptococcus sanguis and Streptococcus mitis versus chlorhexidine. Methods: the agar diffusion method was used for the antibacterial assay. A study was conducted of 18 samples of microorganisms from the above-mentioned species, isolated from patients cared for at a dental clinic. Six different concentrations were prepared of the aqueous extract to compare antibacterial activity versus the chlorhexidine gargle. Preliminary phytochemical analysis was conducted by drop assay. The data obtained were subjected to statistical analyses such as mean and dispersion estimators, unifactorial analysis of variance and Tukey's test. Results: the highest antibacterial activity against the three species of Streptococcus was obtained with the 400 mg/ml concentration, and the lowest with the 25 mg/ml concentration of the aqueous extract, in comparison with chlorhexidine, with a similar effect to the 200 mg/ml concentration. The preliminary phytochemical assay revealed the presence of flavonoids, tannins, steroids, anthocyanins and saponins. Conclusions: the aqueous extract of Pelargonium peltatum has antibacterial activity against Streptococcus mutans, Streptococcus mitis and Streptococcus sanguis.