Nursing behavior in domestic pigs differs between the colostral period and later lactation. During the initial period of colostrum production, the sow passively exposes her udder and thus gives newborn piglets the opportunity to freely arvest colostrum by moving from teat to teat. Nursing behavior in swine is particularly complex because of specific features including nursing synchronization, non-nutritive nursings, the potential for allo-suckling, ontogenetic shifts in nursing initiation and termination, and the balance between the sow-litter and piglet-piglet cooperation and conflict. Acoustic, olfactory and tactile communication play pivotal role in the nursing interactions. The physiological control mechanisms of milk production and milk ejection determine many aspects of nursing behavior but, on the other hand, nursing behavior has a strong feedback influence on physiology, including the hormonal state, of the lactating sow. The functional view on nursing behavior, based on the evolutionary theory-inspired question ´what survival/ reproduction benefit does the behavior bring to the animal?´ can provide important insights into the links between different features of nursing behavior.