Anti-gingipain IgY (IgY-GP), known as hyperimmune γ-livetin from egg yolk, inhibits the enzyme activity, growth and adherence of Porphyromonas gingivalis to gingival epithelial cells. Our objective was to evaluate the effica-cy of IgY-GP on periodontal health of dogs. IgY-GP was prepared from the egg yolk of hens immunized with the gingipain from Porphyromonas gingivalis ATCC 33277. Two in vivo trial models were conducted on 15 adult dogs with periodontitis by giving IgY-GP-sup-plemented dog feed for 8 weeks and direct application of the IgY in dental ointment to the periodontal pockets at weekly interval for 4 weeks. Clinical parameters including gingivi-tis, periodontitis, oral health index, bleeding on probe (BOP), pocket depth (PD), and dental calculus removal pattern for selected premolar teeth were recorded at baseline, 4 and 8 weeks post treatment.IgY-GP showed strong cross-reactivity with gingipain from Porphyromonas gulae and inhibited the enzyme activity in vitro. In the dog trials, IgY-GP resulted in sig-nificant improvement of oral health parame-ters including gingivitis and periodontitis scores, BOP, dental calculus removal. No adverse events during and after antibody appli-cations were noted. Oral immunotherapy by using IgY-GP is a new promising alternative to conventional preventive and therapeutic meth-ods to improve oral health status in dogs.