Protein digestibility has been estimated in dog when fed on two similar diets except their lipid quality (virgin olive oil and sunflower oil) from weaning up to 6 months of life. Experiments were carried out at 60, 105 and 150 days of adaptation to either diet. In dog, age does not seem to affect the protein digestive and metabolic utilization when fed on a high lipid content diet. A higher dietary fat percentage led to an increase of the mentioned parameters which could be caused to a delayed gastric emptying due to fat. As far as the fat quality is concerned, an improved protein digestive and metabolic utilization was evidenced in adult animals fed on olive oil. On the other hand, the weight progress was normal in both experimental groups. These results suggest that olive oil may have beneficial effects on protein digestibility as compared to sunflower oil.