Scaling up effective interventions, policies and programmes can improve breastfeeding (BF) outcomes. Furthermore, considerable interest exists in learning from relatively recent successful efforts that can inform further scaling up, with appropriate adaptations, across countries. The purpose of this four-country case studies analysis was to examine why and how improvements in BF practices occurred across four contrasting countries; Burkina Faso, the Philippines, Mexico and the United States of America. Literature reviews and key informant interviews were conducted to document BF trends over time, in addition to why and how BF protection, promotion and support policies and programmes were implemented at a national level. A qualitative thematic analysis was conducted. The ‘Breastfeeding Gear Model’ and RE-AIM (Reach; Effectiveness; Adoption; Implementation; and Maintenance) frameworks were used to understand and map the factors facilitating or hindering the scale up of the national programmes and corresponding improvements in BF practices. Each of the studied countries had different processes and timing to implement and scale up programmes to promote, protect and support breastfeeding. However, in all four countries, evidence-based advocacy, multisectoral political will, financing, research and evaluation, and coordination were key to fostering an enabling environment for BF. Furthermore, in all countries, lack of adequate maternity protection and the aggressive marketing of the breast-milk substitutes industry remains a strong source of negative feedback loops that are undermining investments in BF programmes. Country-specific best practices included innovative legislative measures (Philippines), monitoring and evaluation systems (United States of America), engagement of civil society (Mexico) and behavior change communication BF promotion (Burkina Faso) initiatives. There is an urgent need to improve maternity protection and to strongly enforce the WHO Code of Marketing of Breast-Milk Substitutes.