The result of Indonesian Household Health Survey showed that 63% of Indonesians suffer from dental caries and periodontal disease. The common forms of periodontal disease are gingivitis and periodontitis. The main cause of periodontitis is bacterial infection from Porphyromonas gingivalis. Porphyromonas gingivalis is an anaerobic gram-negative bacteria that has virulence factor that can infect host and damage normal tissue. Pineapple peel contains flavonoids, bromelain enzymes, and tannins that can act as antibacterial agents. This purpose of this study is to examine the effects of antibacterial power of pineapple (Ananas comosus) peel extract on the growth of Porphyromonas gingivalis in vitro. This research is pure laboratory experimental research in vitro. Subjects in this study were Porphyromonas gingivalis and pineapple peel extract (Ananas comosus). The antibacterial power test was performed by liquid dilution method on Brain Heart Infusion (BHI) medium and solid dilution method on Trypticase Soy Agar (TSA) media. Pineapple peel extract (Ananas comosus) was diluted into several concentrations: 100%, 50%, 25%, 12.5%, 6.25%, 3.125%, 1.56%, and 0.78%. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) are determined by observing the growth of Porphyromonas gingivalis bacteria in both media. MIC is present at a concentration of 12.5%, while MBC is present at 25% concentration. This study can be concluded that pineapple peel extract (Ananas comosus) has antibacterial effect on Porphyromonas gingivalis bacteria.