Dental caries is one of the most prevalent oral diseases worldwide and is closely associated with cariogenic microorganisms, particularly bacteria belonging to the genus Streptococcus. In western Côte d'Ivoire, several medicinal plants are traditionally used as chewing sticks for oral hygiene, although their antibacterial properties remain poorly documented. This study evaluated the antibacterial activity of aqueous and hydro-ethanolic extracts of Mezoneuron benthamianum Baill. and Strychnos afzelii Gilg. against Streptococcus spp. isolated from dental caries. Plant extracts were prepared by maceration in distilled water and 70% ethanol. Antibacterial activity was evaluated using the agar well diffusion method, while the minimum inhibitory concentration and minimum bactericidal concentration were determined using the broth macrodilution method. Hydro-ethanolic extraction produced the highest yields, reaching 17.60% for Mezoneuron benthamianum and 16.90% for Strychnos afzelii. Neither the aqueous nor the hydro-ethanolic extracts of Strychnos afzelii exhibited antibacterial activity against the tested strains. In contrast, both extracts of Mezoneuron benthamianum inhibited the growth of all tested Streptococcus spp., with inhibition zones ranging from 13.00 ± 0.50 mm to 18.00 ± 0.58 mm. The minimum inhibitory concentration and minimum bactericidal concentration were both 25 mg/mL, resulting in a minimum bactericidal concentration to minimum inhibitory concentration ratio of 1, indicating a bactericidal effect. These findings provide experimental support for the traditional use of M. benthamianum as a chewing stick plant and suggest its potential source of antibacterial compounds for future oral health applications.