Streptococcus mutans is recognized as the major causative agent of dental caries, especially in fissures and on smooth surfaces. Thus, the purpose of this study was to evaluate the susceptibility of S. mutans (ATCC 25175) biofilm to photodynamic therapy after sensitization with chlorin e-6 (PS) at 0.6 and 2.5μM by exposure to red light at 660nm (BioTable®) under 36.1mW, 15J/cm2 and 5 min of pre-irradiation time. Biofilm was induced in BHI broth supplemented with 1% sucrose for 7 days in a 96 well-plate. Serial dilutions were seeded onto brain heart infusion agar to determine viability in colony-forming units per milliliter (CFU/mL). Additionally, the metabolism of the biofilm by XTT and confocal laser scanning microscopy (CLSM) was performed using BacLight LIVE/DEAD system. Different groups were analyzed: L-D- (negative control), L-D+ (drug), L+D- (light), L+D+ (PDT) and clhorexidine at 0.2% (positive control). Results were analyzed by two-way ANOVA and Tukey’s test (p<0.05). Biofilms were taken for observation at confocal microscopy, and qualitative analyzes were obtained as to the distribution of non-viable viable/cells using LIVE/DEAD® Baclight™ before and after treatments. For CFU/mL and metabolism, the data were submitted to analysis of variance (ANOVA) and Tukey's test at 5% significance. It was observed that there was statistically significant difference in all PDT and chlorhexidine Groups compared to negative control and light Group (p<0.05). No dark cytotoxicity was observed (p>0.05). PDT using chlorin e-6 as photosensitizer can be an adjunct and effective method to control Streptococcus mutans biofilm responsible to dental caries.