B Background: Periodontal disease is one of the major dental and oral health problemsin Indonesia. The primary bacteria causing periodontal disease are Porphyromonasgingivalis and Treponema denticola. Chlorhexidine commonly used for periodontaltherapy, but its long-term use can cause side effects such as burning sensations in themouth, tongue discoloration, and mucosal irritation. Herbal-based therapies can serveas alternative periodontal treatments. Alstonia scholaris leaves contain bioactivecompounds that are effective as antimicrobial, antioxidant, and anti-inflammatoryagents. Objectives: To investigate the antibacterial and antibiofilm effects of Alstoniascholaris methanol extract against Porphyromonas gingivalis and Treponemadenticola, which are the causative agents of periodontal disease. Methods: The testsolutions used included Alstonia scholaris methanol extract at concentrations of 100%,50%, 25%, 12.5%, 6.25%, and 3.125%, chlorhexidine 0.2% as a positive control, anddistilled water as a negative control. Antibacterial testing was conducted using theagar dilution method to determine inhibitory and bactericidal activities. Antibiofilmtesting was performed using the microtiter plate biofilm assay method. Results: Themethanol extract of Alstonia scholaris effectively inhibited the growth ofPorphyromonas gingivalis and Treponema denticola at a concentration of 12.5%,effectively killed these bacteria at a concentration of 25%, effectively inhibited biofilmformation of Porphyromonas gingivalis at 12.5%, and effectively inhibited biofilmformation of Treponema denticola at 50%. Conclusion: The methanol extract ofAlstonia scholaris has been proven effective as an antibacterial and antibiofilm agentagainst Porphyromonas gingivalis and Treponema denticola.