The objective of this study was to analyze quantitatively whether Weissella cibaria could affect the proliferation of five periodontopathic bacteria, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum, after incubation for 8~48 h. In addition, by using real-time PCR with a dual-labeled probe, each growth of bacteria was examined under different growth media conditions. The proliferation of periodontopathic bacteria was significantly inhibited by W. cibaria after incubation for 24~48 h (p < 0.05), whereas the growth of W. cibaria was not affected by these pathogenic bacteria. The growth of P. gingivalis, T. forsythia and T. denticola significantly increased in each growth media after incubation for 24 h (p < 0.05), as compared to the culture in mixed growth media. However, no differences in the growth of five periodontopathic bacteria were observed between each growth media and mixed media after incubation for 48 h. The growth and pH of W. cibaria culture significantly were changed in MRS after incubation for 24~48 h (p < 0.05), as compared to the bacterial culture in mixed growth media. The pH of P. gingivalis and F. nucleatum culture significantly was changed in both growth media and mixed media after incubation for 24~48 h (p < 0.05). Our data indicate that W. cibaria significantly inhibits the proliferation of five periodontopathic bacteria and each growth of bacteria is quantitatively analyzed under various media conditions by real-time PCR.