We study the effect of family income and maternal hours worked on child development. Our instrumental variable analysis suggests different results for cognitive and behavioral development. An additional $1,000 in family income improves cognitive development by 4.4 percent of a standard deviation but has no effect on behavioral development. A yearly increase of 100 work hours negatively affects both outcomes by approximately 6 percent of a standard deviation. The quality of parental investment matters and the substitution effect (less parental time) dominates the income effect (higher earnings) when the after-tax hourly wage is below $13.50. Results call for consideration of child care and minimum wage policies that foster both maternal employment and child development.