Aims To investigate the effects of the ginsenoside Rh2 on monospecies and multispecies cariogenic biofilms and explore the mechanism of the antibiofilm effect of Rh2 in vitro. Methods and Results Streptococcus mutans, Streptococcus sobrinus and Streptococcus sanguinis were chosen to form the monospecies or multispecies biofilms. Crystal violet staining and laser scanning confocal microscopy were used to observe the effect of Rh2 on biofilms in vitro. Cytotoxicity was examined by the Cell Counting Kit-8. The effects of Rh2 on bacterial membranes were observed via transmission electron microscopy (TEM). The isobaric tags for relative and absolute quantification (iTRAQ) method were used to profile the common differentially expressed proteins. Gene expression was analysed by reverse transcription quantitative polymerase chain reaction. In general, the treatment of cariogenic biofilms with Rh2 significantly decreased biomass accumulation by inhibiting bacterial growth and extracellular polysaccharide synthesis without any cytotoxic effects. TEM imaging showed that Rh2 could disrupt the cell membranes of these bacteria. The iTRAQ results indicated that the levels of mannose-specific IIC/D and acetaldehyde/alcohol dehydrogenase were substantially down-regulated, while the mRNA expression of the corresponding genes were significantly changed. Conclusions Our data revealed a potential application for Rh2 in the protection against dental caries via the inhibition of cariogenic biofilms. Significance and Impact of the Study: This study describes the first application of a ginsenoside against multispecies cariogenic biofilms. Rh2 may serve as an alternative agent to prevent dental caries by effectively modulating the pathogenic potentials of oral biofilms.