Aim: To determine the effectiveness ofLactobacillus rhamnosusin inhibiting halitosis-causing bacteria relative to other possible inhibitors, such as mouthwashes.Materials and Methods: This in vitro study was done using a diffusion test with three groups with 11 samples in each group: group A,Porphyromonas gingivalis; group B,Tannerella forsythia; and group C,Prevotella intermedia. At 24, 48, and 72 hours, the inhibitory effect ofL. rhamnosuswas tested.Results: A statistically significant difference was seen for halo formation in group A, where all 11 samples showed an inhibitory effect after 72 hours. After 48 hours, seven of the 11 samples in group B and nine of the 11 samples in group C showed inhibitory effects.Conclusion: The study found thatL. rhamnosushad an inhibitory effect on halitosis-causing bacteria likeP. gingivalisafter 72 hours, which was statistically significant. The same was true forT. forsythiaandP. intermediaafter 48 hours. This means thatL. rhamnosushas an inhibitory effect on halitosis-causing bacteria likeP. gingivalis.