The authors examined children's sleep as an intervening variable in the connection between emotional insecurity in the family and academic achievement. The role of ethnicity (African American and European American) and socioeconomic status (SES) in moderating the examined relations was assessed. One hundred sixty-six children (8- and 9-year-olds) reported their emotional insecurity, and the quantity and quality of children's sleep were examined through actigraphy and self-report. Decreased amount and quality of sleep were intervening variables in the relations between insecurity in the marital relationship and children's achievement. The effects of disrupted sleep on achievement were more pronounced for both African American children and children of lower SES. Results highlight the importance of the contemporaneous examinations of family and sleep functioning in the prediction of child outcomes.