Implications of family economic conditions (FECs) for child development have been extensively examined. What remains sparse is research spanning multiple life stages to delineate the far-reaching influences of early FECs for child subsequent development in different domains and how various family stress and investment processes jointly account for such association. To address these gaps, using data from 929 families in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (NICHD Early Child Care Research Network, 2001, 2005), this study examined how family income-to-needs ratio (FITNR) when children were 1–36 months old was associated with child language skills, social competence, externalizing, and internalizing problems at 6th grade. Parental investment and maternal/paternal depressive symptoms and sensitivity when children were 54 months old and in 3rd grade were tested as potential mediators. Results indicated that early FITNR shaped child cognitive, social, and behavioral adaptation in early adolescence indirectly through parental investment, depressive symptoms, and sensitive parenting in the preschool period and middle childhood. Parental investment, depressive symptoms, and sensitive parenting played such mediating roles above and beyond each other. Parental investment primarily accounted for the association between early FITNR and child later language skills, whereas parental depressive symptoms and sensitive parenting uniquely explained the associations between early FITNR and child subsequent internalizing symptoms, externalizing problems, social competence, and language skills. Theoretical/practical implications of such findings were discussed.