This research is aimed at investigating the in vitro antimicrobial activities of Jatropha curcas twigs against dental carries-causing bacteria. The methanol/methyl chloride crude extract of J. curcas twigs was fractionated into aqueous, n-hexane, ethyl acetate and n-butanol fractions. Using the agar well diffusion and the agar dilution methods, the antimicrobial activities of plant fractions were determined against strains of Streptococcus mutans isolated from dental swabs from patients with dental caries. The ethyl acetate fraction showed best antimicrobial activity with a minimum inhibitory concentration (MIC) of 6.25 mg/ml, followed by the n-butanol and n-hexane fractions, both with MICs ≥ 25 mg/ml against S. mutans. The aqueous fraction showed no activity against all strains of S. mutans tested. The results of our study show that J. curcas twig possesses antimicrobial against dental caries-causing bacteria strains. This justifies the folkloric use of the plant twigs in oral hygiene as a chewing stick/toothbrush for the prevention of dental caries.