ObjectivesThe aim of this study was to evaluate the addition of chitosan nanoparticle with concentrations of 0, 10, 20, and 30% to the epoxy resin-based (ERB) sealer on its antibacterial and cytotoxicity effect.Methods and MaterialsThis research was divided into two studies, the first study was the addition of chitosan with a concentration of 0% (as control), 10, 20, and 30% to an ERB sealer on its antibacterial effect, and the second study was on its cytotoxicity. An agar diffusion test was employed to determine the antibacterial effect onEnterococcus faecalis. An MTT (3-{4,5-dimethylthiazol-2-yl}-2,5-diphenyl tetrazolium bromide) assay was utilized to test the cytotoxicity by evaluating cell viability.Statistical AnalysisOne-way analysis of variance and Tukey's test (α= 0.05) were used to analyze data obtained from each evaluation with a significance level of 95%.ResultsThe addition of chitosan nanoparticles at concentrations 10, 20, and 30% produced a greater inhibition zone ofE. faecalis(p< 0.05), however, had less cytotoxicity compared with no addition of chitosan (0%) (p< 0.05).ConclusionThe addition of chitosan nanoparticles at concentrations 10, 20, and 30% to the ERB sealer produced greater antibacterial and less cytotoxicity compared with no addition of chitosan (0%).