In this study, we examined the developmental pathways from children's family environment to school readiness within a low-income sample (N = 1,046), with a specific focus on the role of sustained attention. Six distinct factors of the family environment representing maternal parenting behaviors, the physical home environment, and maternal mental health at 3 years of age were explored as independent predictors of children's observed sustained attention as well as cognitive and behavioral outcomes at 5 years of age. Children were grouped by poverty status (poor vs. near-poor). Results suggest specificity in the associations among attention (focused attention and lack of impulsivity) and its correlates, with different patterns emerging by poverty status group. Overall, the family environment was largely unrelated to children's sustained attention. For both groups, focused attention was associated with receptive vocabulary; however, it partially mediated the association between maternal lack of hostility and receptive vocabulary only among the near-poor. In addition, lack of impulsivity was associated with both receptive vocabulary and externalizing behaviors but only for the poor group. Findings indicate sustained attention as a potential target for efforts aimed at enhancing school readiness among predominantly poor children.