Importance: There is convincing evidence that breastfeeding provides substantial health benefits for children. However, nearly half of all US mothers who initially breastfeed stop doing so by 6 months, and there are significant disparities in breastfeeding rates among younger mothers and in disadvantaged communities. Objective: To update the 2008 US Preventive Services Task Force (USPSTF) recommendation on primary care interventions to promote breastfeeding. Evidence Review: The USPSTF reviewed the evidence on the effectiveness of interventions to support breastfeeding on breastfeeding initiation, duration, and exclusivity. The USPSTF also briefly reviewed the literature on the effects of these interventions on child and maternal health outcomes. Findings: The USPSTF found adequate evidence that interventions to support breastfeeding, including professional support, peer support, and formal education, change behavior and that the harms of these interventions are no greater than small. The USPSTF concludes with moderate certainty that interventions to support breastfeeding have a moderate net benefit. Conclusions and Recommendation: The USPSTF recommends providing interventions during pregnancy and after birth to support breastfeeding. (B recommendation).