The aim of this study was to determine the antibiotic susceptibility of subgingival bacteria in dogs with moderate to severe periodontal disease. Thirty dogs from four shelters were sampled using sterile paper sheet tips at the bottom of the periodontal pocket in the fourth premolar and canine teeth of the upper right quadrant. The mostfrequent bacteria isolated were Porphyromonas gingivalis (50%), Bifidobacterium spp (20%), Prevotella intermedia (16.7%), Staphylococcus spp (30%) and enterobacteria (60%). The highest antibiotic susceptibility from isolated bacteria species was against imipenem. The susceptibility against other antibiotics depended of the bacterial species.