Background: Dental caries is an infectious disease related to biofilm formation. Among the microorganisms presents in the oral microbiota, Streptococcus mutans can form biofilm on the tooth surface in the presence of dietary carbohydrates. This study aimed to evaluate the bactericidal kinetics and antibiofilm efficacy of ent-pimara-8(14),15-dien-19-oic acid (compound 1) and ent-8(14),15-pimaradien-3β-ol (compound 2) obtained from Viguiera arenaria against oral pathogens; this study also aimed to determine the effect of these compounds on the morphology and architecture of the S. mutans biofilm by scanning electron microscopy (SEM). Materials and Methods: The bactericidal kinetics revealed different results depending on the tested bacteria. Compound 1 eliminated the viable bacteria within 24 hs of incubation. In the antibiofilm assay, compound 1 displayed promising results against S. mitis (ATCC 49456 and clinical isolate) and L. casei (clinical isolate), whereas compound 2 was not active at the evaluated concentrations. Conclusion: Compound 1 is an important metabolite in the search for new antibacterial agents against cariogenic bacteria both in the sessile and planktonic modes. The SEM image of Streptococcus mutans in the presence of compound 1 suggested that this metabolite acts by disrupting the bacterial membrane disrupting the bacterial membrane and/or cell wall and causing microrganism death.