Abstract: The aim of this study was to investigate the anti-cariogenic effects of the indigenous Iranian medicinal plant Alcea longipedicellata (Malvaceae), to inhibit the growth and acid production of Streptococcus mutans and other cariogenic bacteria involved in dental plaque. The growth inhibitory activity of the ethanol and chloroform extracts were tested against S. mutans, S. salivarious, S. sobrinus and S. sanguis. From an ethanol extract of A. longipedicellata flowers, malvidin-3,5-diglucoside (malvin) was identified as a principal constituents which was responsible for antibacterial activity of extract. The malvin showed bacteriocidal activity, while ethanol and chloroform extracts was bacteriostatic. The MIC value of the malvin was 0.16-0.22 mg mL-1. In vitro studies had shown that 0.1% malvin could inhibit strongly acid-producing ability of S. mutans and salivary glycolysis up to 2 h post rinsing and reduced total bacterial counts of saliva up to 40% 3 h post rinsing. 0.1% malvin was about 60% effective in inhibiting bacterial adherence, as shown by the low weight of accumulated S. mutans plaque to glass surface. In conclusion, the anti-acidogenic effect of A. longipedicellata suggests that this material could be a useful source for the development of promising anti-cariogenic agents and led to use for pharmaceutical preparations such as mouth rinse.