The aim of this study was to examine the associations between sleep and neurobehavioral functioning (NBF) in school-age children. These variables were assessed for 135 unreferred, healthy school children (69 boys and 66 girls), from second-, fourth-, and sixth-grade classes. Objective assessment methods were used on the participants in their regular home settings. Sleep was monitored using actigraphy for 5 consecutive nights; and NBF was assessed using a computerized neurobehavioral evaluation system, administered twice, at different times of the day. Significant correlations between sleep-quality measures and NBF measures were found, particularly in the younger age group. Children with fragmented sleep were characterized by lower performance on NBF measures, particularly those associated with more complex tasks such as a continuous performance test and a symbol-digit substitution test. These children also had higher rates of behavior problems as reported by their parents on the Child Behavior Checklist. These results highlight the association between sleep quality, NBF, and behavior regulation in child development; and raise important questions about the origins of these associations and their developmental and clinical significance.