Objective: This study aimed to determine the effect of ethanol Curcuma extract on the viability of S. mutans and Streptococcus sanguinis in a dualspecies in vitro biofilm model. Methods: Dual-species biofilms of S. mutans and S. sanguinis were exposed to ethanol Curcuma extract at various concentrations. The sample of saliva was gathered from healthy volunteers. Chlorhexidine 0.2% was used as a positive control, and bacterial culture without intervention served as a negative control. The total suspensions of 10−as were prepared for S. mutans and S. sanguinis cells. The bacteria were incubated for 20 h (active maturation phase) and 24 h (maturation phase). Results: The result showed decreased S. mutans and S. sanguinis viability after exposure to 0.2%–25% Curcuma ethanol extracts during the active accumulation and maturation phases. The decrease in bacterial viability was significantly different in all concentrations of Curcuma ethanol extracts compared with negative controls (p<0.05) in the active accumulation and maturation phases. Conclusion: Temulawak ethanol extract (starting at 0.2%) can decrease the viability of S. mutans and S. sanguinis in a dual species in vitro biofilm model during the accumulation and maturation phases. © 2019 The Authors.