B ackground: Periodontitis is an irreversible periodontal disease which has involved attachment apparatus. Fusobacterium nucleatum and Treponema denticola are bacteria that cause periodontal disease. The primary treatment for periodontal disease is to remove bacteria through plaque control. Plaque control can be done mechanically using tooth brush and interdental cleaning aid assisted with chemically method using antibacterial mouthwash. Kepok banana peel (Musa paradisiaca formatypica) contain chemical compound that proven to have an antibacterial activity. Kepok banana peel extract contains saponin, flavonoid, and triterpenoid that can inhibit the bacteria growth. Objective: To determine the effectiveness of kepok banana peel as an antibacterial inhibitor against F. nucleatum and T. denticola. Methods: The experimental laboratory study with microdilution method, using F. nucleatum ATCC 25586 and T. denticola ATCC 35405. The material used was kepok banana peel extract with 6 concentrations 30%, 25%, 20%, 15%, 10%, and 5%. The antibacterial test was carried out by counting the total bacterial colonies obtained by using the formula for the mean total colony of bacterial colonies. Results: In the kepok banana peel extract test against F. nucleatum, minimal inhibitory concentration is obtained at concentration of 20% and minimal bactericidal concentration is obtained at concentration of 30%. In the kepok banana peel extract test against T. denticola, minimal inhibitory concentration is obtained at concentration of 10% and minimal bactericidal concentration is obtained at concentration of 25%. Conclusion: Kepok banana peel extract is effective in inhibiting the growth of F. nucleatum at concentration of 30% and T. denticola at concentration of 25%.