Behavioral interventions had statistically significant positive effects on maternal mental health and breastfeeding and most showed a decrease in self-reported depression and/or anxiety symptoms in parallel with an increase in breastfeeding duration and/or exclusivity. Successful interventions shared the following characteristics: hospital staff or multidisciplinary teams delivered them, they were offered individually, they focused on breastfeeding and maternal mental health or on breastfeeding only, and they took place during pregnancy and postpartum.