Breast milk is the best food for the neonate because it provides a unique combination of proteins, carbohydrates, lipids, minerals and vitamins that ensures the correct growth and development of the infant. In addition, it also contains bioactive compounds responsible for a wide range of beneficial effects such as the promotion of immune system maturation and the protection against infections. Among these bioactive agents, probiotic bacteria have been recently isolated from human milk. The present work reviews the beneficial effects of these bacteria both in animal models and in clinical trials. The promotion of immune system maturation and defence against infections as well as the anti-inflammatory properties are among the main healthy effects of these bacteria. The isolation of probiotic bacteria with beneficial effects for the host provides scientific support for the supplementation of infant formula with these bacteria, in order to advance the pursuit of the main goal of formula: to mimic breast milk and its functional effects as closely as possible.