Puppies start eating food at approximately four weeks of age. The food should be introduced as a sort of mush that is a blend of the food the mother is on, puppy milk replacement, and hot water. You just mix those three things together in a blender to make the consistency of human infant cereal. Then each week you can increase the amount of food and decrease the amount of liquid until the 8th week. By then your puppy should be able to eat regular puppy food.