Migration theory is adult-centric, failing to account for the experiences of children despite their increasingly important participation in migration flows. Using a life-course perspective and findings from research at the intersection of childhood studies and migration, this paper considers whether different migration theories apply to child migration as compared to adult migration. We examine this question using the Mexican Migration Project data to track the cross-border moves of 109,096 individuals relative to their family members. We find that theories from economics best explain migration among young adults, with some participation from older adolescents, while children of all ages are sensitive to educational opportunities and the behavior of their peers and role models. Insights from the cultural turn and feminist theorizing in migration studies explain migration for both groups. We find that adult and child migration is strongly conditioned on migrant networks and family dynamics, including ties to family members in destination and family structure and caretaking arrangements in origin. We argue that child-centered analyses advance migration theory by highlighting the role of age, the life-course, and intergenerational family dynamics as determinants of international migration.