Objective: This study aimed to compare the effect of Curcuma xanthrorrhiza ethanol extract to the viability of Streptococcus mutans and Aggregatibacter actinomycetemcomitans using single-and dual-species biofilm at different phases of formation.Methods: Biofilm models were incubated for 4, 12, and 24 hrs, then exposed to the extract at a concentration of 0.525%. Results:The viability of the single-species S. mutans biofilm was low (p<0.05), and no significant difference (p>0.05) was found between singlespecies A. actinomycetemcomitans and dual-species biofilm. Conclusions:Curcuma xanthorrhiza ethanol extract is more effective for decreasing the viability of single-species S. mutans biofilm.