Family processes and parenting practices help explain developmental differences between children in low- versus higher-income households. There are, however, few studies addressing the question of: what are the key family processes and parenting practices for promoting low-income children’s growth? We address this question in the present study, following conceptual work framing family processes and parenting practices as investments in children. Using secondary analyses of longitudinal data on low-income children from birth to age 15 (n = 528), we estimate several potential family investments in achievement and socioemotional outcomes during early childhood, middle childhood, and adolescence. For achievement outcomes, family investments in learning stimulation were consistently the strongest predictors. For socioemotional outcomes, investments in an orderly household and close parental supervision were the most consistent and strongest predictors, even more so than sensitive parenting.