This study aimed to investigate how mothers and infants contribute mutually to breastfeeding. The spontaneous interactions of 20 breastfeeding dyads were video-recorded at home, at 2, 4, 6, 9 and 12 months of infants' life. Mothers' and infants' gaze and tactile behaviour, facial expressions of emotion, and dyadic expressions were continuously micro-analysed. Results showed that a) the developmental patterns of maternal and infant expressive behaviours reflected age-related variations in the way infants regulate their feelings and express their interests to their companions; b) maternal gaze and tactile behaviour, infant's negativity, and participation in a shared activity, were correlated to the breastfeeding duration. Our observations may help health care professionals to support breastfeeding through the facilitation of mother-infant communication.