Aim: The aim of this study was to comparatively evaluate the antibiofilm efficacy of Mimosa pudica L. and chlorhexidine (CHX) against Streptococcus mutans (S. mutans) as a mouthrinse. Methods: S. mutans were cultured from saliva collected from high caries risk patients and inoculated in Mueller–Hinton agar plates. The mouthrinses were grouped as follows: group I—10% aqueous extract of M. pudica L. mouthrinse, group II—0.2% CHX mouthrinse, and group III—saline. The resazurin-based dye microbroth assay was used to check the effect of test rinses on the redox activity of salivary bacteria and optical density (OD) values were recorded. Biofilm was grown on the surface of enamel slabs for 7 days in an anaerobic work station using S. mutans and treated with respective mouthrinses for 2 minutes at room temperature. The slabs were stained using fluorescent dye propidium iodide and SYTO9 and visualized under confocal scanning laser microscopy (CLSM) and qualitatively analyzed for live/dead bacteria. The percentage of viability was determined and statistically analyzed using the one-way analysis of variance (ANOVA) test at the p-value of <0.05. Results: Based on OD values of resazurin-based dye assay and CLSM analysis, group II showed higher antibacterial efficacy with significant differences than groups I and III. Conclusion: The percentage of biofilm inhibition was found to be less for aqueous extract of M. pudica L. than CHX. However, it is evident that M. pudica L. can resist the oral cariogenic bacteria, thereby preventing the formation of dental caries.