Background: Enterococcus faecalis is the main reason that caused of periradicular after root canal treatment. Currently being encouraged by using the natural ingredients as an alternative substance of tooth root canal irrigation. One is the peel of red dragon fruit (Hylocereus polyrhizus) containing flavonoids, tannins, and alkaloids. Purpose: To know the antibacterial againts of the peel of red dragon fruit extract (Hylocereus polyrhizus) to the growth of bacterium Enterococcus faecalis. Method: This research is an experimental laboratory research in vitro using bacterium Enterococcus faecalis ATCC 2921. The method used is ditch-diffusion on Mueller Hinton media to continue the measurement of radical zone by using sliding caliper. The peel of red dragon fruit extract (Hylocereus polyrhizus) consists of several concentrations: 20%, 40%, 60%, 80%, 100% based on V1N1 = V2N2. Result: All tested concentrations have the antibacterial againts the growth of Enterococcus faecalis bacteria. The highest concentration of antibacterial againts was 100% (p <0.05). Conclusion: Peel of red dragon fruit extract (Hylocereus polyrhizus) has antibacterial againts to the growth of Enterococcus faecalis bacteria.