Background/Aims: For mothers in high-income country contexts, infant feeding represents one of the most fundamental and challenging aspects of the transition to parenthood. We present a specific theoretical model, based on life course theory principles, to explicate how the maternal ecology influences breastfeeding behaviors throughout the early parenting years. Methods: Core concepts and suppositions draw from a review of extant theories for the development of infant feeding behaviors, including intraindividual models of health behavior and bioecological models of human development. We highlight where the model has strong evidentiary support and where there are gaps in the literature. Results: This review shows how life course theory has been used to describe the consequences of infant feeding behaviors, but has yet to be fully applied to the causes of those behaviors. The natural extension of life course theory to include these constructs and relationships will extend the field of breastfeeding research. Breastfeeding intervention could also be strengthened with more recognition of the life course factors that represent understudied, and thus underutilized, levers for intervention. Conclusion: Given its focus on personal history in a larger historical and ecological context, life course theory is well suited to framing discussions around the causes and consequences of breastfeeding.