Abstract : Oral biofilms can cause a health-related problem in the mouth cavity. The purpose of this study was to determine antibacterial and antibiofilm effects of quercetin on two oral microbes, S. sanguinis and S. mutans in anaerobic condition. The antibacterial was assayed with microdilution method in aerobic condition. The antibiofilm activity was assayed using microdilution method in an anaerobic environment by using crystal violet as an indicator. SEM (Scanning Electron Microscopy) analysis was conducted to observe biofilms on the surface coverslip. The result showed MIC50 (Minimum Inhibition Concentration) of quercetin on S. sanguinis and S. mutans was 0.125% v/v. MBIC50 (Minimum Biofilm Inhibition Concentration) of quercetin was 1% v/v on S. sanguinis and S. mutans. MBEC50 (Minimum Biofilm Eradication Concentration) of quercetin on S. sanguinis was 1% v/v and was observed at 0.25% v/v on S. mutans. Based on the research conducted, it can be concluded that quercetin has a degradation effect on S. sanguinis and S. mutans. SEM analyses confirmed that quercetin demonstrated degradation effect to S. sanguinis and S. mutans. Noteworthy to evaluate the quercetin effect towards polymicrobial biofilms