The capacity of children to act as agents is being increasingly recognized and has important implications for health research and practice. However, there are various discrepancies in how children’s agency is defined in the literature. The aim of this analysis was to examine the concept of children’s agency within the health-related literature, using Rodgers evolutionary method. The following questions were addressed: How did the concept of agency become associated with children in the health-related literature? What are the sociocultural and legal contexts that surround the concept of children’s agency? What is the meaning of children’s agency? Forty-five articles were included in the analysis. An inductive approach was used to identify the attributes of children’s agency as well as the temporal, disciplinary, and paradigmatic trends in its conceptualization. The concept of children’s agency first appeared in the health literature in the 1980s and was defined as an ability children could gradually develop. Later on, children’s agency was used to refer to the capacity of all children to influence their own and others’ health-care needs and is now increasingly used to refer to children as active agents who reflect on and construct their social worlds.