Background: The FimA of Porphyromonas gingivalis is a crucial pathogenic component of the bacteria and has been implicated as a target for vaccine development against the periodontal diseases. Methods: In this study, the purified fimbriae (FimA subunit polymers) protein was used for immunization in their native form and B hybridoma clones producing antibodies specific to FimA were established. Results: The monoclonal antibodies prepared from selected two clones, designated #123 (IgG2b/ kappa) and #265 (IgG1/kappa), displayed different patterns of binding activity against the cognate antigen. Both antibodies reacted with conformational epitopes expressed by partially dissociated oligomers, but not with monomer as elucidated by Western blot analysis. Ascites fluid containing the monoclonal antibodies showed the inhibitory activity against P. gingivalis to saliva-coated hydroxyapatite beads, an in vitro model for the pellicle-coated tooth surface. Conclusion: These results suggest that the monoclonal antibodies could be used as vaccine material against the periodontal diseases through passive immunization.