AbstractProbiotics are micro‐organisms that confer health benefits on the host. Postulated mechanisms include: increasing resistance of the mucosal barrier to migration of bacteria and their toxins by strengthening intestinal cell junctions, modification of host response to microbial products, augmentation of immunoglobulin A mucosal responses, enhancement of enteral nutrition to inhibit the growth of pathogens; production of antimicrobial proteins; and competitive exclusion of potential pathogens. Published meta‐analyses and systematic reviews report the effects of probiotics on important clinical outcomes in neonates. This paper will review the evidence for probiotic supplementation in neonatology, with a focus on preterm infants.