Streptococcus mutans is a principal pathogenic agent in biofilm formation on the teeth surfaces and subsequently development of dental caries and plaque. Therefore, currently introducing novel anti-bacterial and anti-biofilm agents, especially plant based materials are highly regarded. This study was planned to investigate in silico and in vitro antibacterial activities of Prangos acaulis extracts against S. mutans in single and biofilm forms and their mutagenicity in Ames test.Methods: The anti-bacterial and anti-biofilm effects of methanol extracts from various parts of P. acaulis were evaluated using disk diffusion and microtiter assay. Moreover, the potential mutagenicity of the extracts was investigated using Ames test. In addition, dominant constitutes of P. acaulis that reported in previous studies were subjected to an in silico analysis. The ability of selected phytochemicals to inhibit the glucosyltransferase was evaluated using molecular docking method.Results: All tested extracts especially root extract had significant antibacterial activity against the single form of S. mutans and inhibited biofilm formation without any mutagenic activity. The results also confirmed that three compounds consisting of ar-curcumene, d-limonene and alpha-pinene had strong and appropriate interactions to glucosyltransferase.Conclusion: This study indicated that P. acaulis has potent antibacterial and biofilm inhibition activity against S. mutans and can be good candidate for in vitro and in vivo studies with the aim of introducing novel inhibitors of dental caries development.