In the human oral cavity, Streptococcus mutans is often observed and is a major contributor to tooth decay. Increased S. mutans levels may be linked to progressively more severe forms of periodontal disease because root exposure in people with periodontitis increases caries rates. Hence, a new potential antibacterial compound needs to be searched to combat this pathogenic bacterium. The butterfly pea, or Clitoria ternatea is an ornamental plant that has been reported to exhibit antibacterial properties against several bacteria. Thus, the goal of this investigation was to determine how well C. ternatea aqueous (CTA) extract inhibited S. mutans. The disk diffusion assay was performed to access the antibacterial properties of the CTA extract. The efficiency of the extract against the test bacterium was then determined through MIC/MBC determinations and a time-kill study. Meanwhile, the toxicity of the extract was tested using a brine shrimp lethality assay (BSLA). The CTA extract demonstrated substantial antibacterial activity against the test bacterium at a concentration of 200 mg/ml, with a diameter of the inhibition zone of 13.4±0.4 mm, according to the disc diffusion assay. The aqueous extract’s MIC and MBC values were found to be 100 and 400 g/mL, respectively. Time-kill analysis revealed the CTA extract exerted a strong bactericidal effect on S. mutans and this activity was dose-dependent. A scanning electron microscope (SEM) exhibited the bacterial cells experienced severe damage after being exposed to CTA extract including formation cavities, irregular shape, and crumpled cells. Thus, the present study suggested the potential of CTA extract as an antibacterial agent against oral cavity bacteria and can be used in the formulation of natural mouthwash due to no toxicity effect.