The objective of this study was to investigate the effects of supplementation of tea polyphenols (TP) in dry dog food on the palatability of dry dog food, serum oxidative stress biomarkers, and fecal pathogenic bacteria in adult dogs. Four different concentrations of TP (0.25%, 0.50%, 0.75% and 1.0%) were added to the basal dog food before or after extrusion. The TP retention rate before extrusion was more than 80% and significantly higher than that after extrusion (<60%). First-choice ratios of palatability were 72%, 68% and 70% for TP concentrations of 0.50%, 0.75% and 1.0%, respectively, resulting in significant increases compared to the palatability for the control of 28%, 32% and 30%. The intake ratio (one-pan test) and consumption ratio (two-pan test) of the 0.50% TP experimental dog food were 73% and 74%, respectively, significantly higher than the other three TP supplemented foods. The serum total antioxidant capacity, superoxide dismutase activities and glutathione peroxidase activities determined in the dogs' food of 0.50% TP group increased by 19.30%, 7.72% and 4.64%, as compared to the control group after 12 weeks, respectively. The serum malondialdehyde concentration was reduced by 15.05%. The fecal aerobic plate count and Coliform bacteria MPN (most probable number) of 0.50% TP group decreased by 2 logs and 1 log, respectively, compared with the control group after 12 weeks. The findings of this study have demonstrated that a concentration of 0.50% TP added to the dry dog food can significantly increase the palatability, antioxidant capacity and antibacterial activity of dry dog food in the canine model.