1. When to start adding baby complementary foods In the first six months after the baby is born, breast milk or formula milk powder can provide all the nutrients the baby needs. Therefore, according to the recommendations of the World Health Organization, complementary foods should be introduced to the baby 6 months after birth. If you choose to introduce solid foods between 4 and 6 months of age, talk to your pediatrician first. 2. How to start adding complementary foods to your baby. When you are ready to introduce complementary foods to your baby