To gain a better understanding of relations between marital aggression and children's sleep problems, we examined children's emotional insecurity as a process variable and a moderator of effects using 3 waves of data spanning 5 years. Participants were 176 children at Time 1 (T1; M age = 8.68 years), 141 children at Time 2 (T2; M age = 10.70 years), and 113 children at Time 3 (T3; M age = 13.60 years) and their parents. Parents reported on marital aggression, children reported on their emotional insecurity about the parental marital relationship, and children's sleep was measured via self-reports and actigraphy. After controlling for autoregressive effects, marital aggression predicted increases in emotional insecurity 2 years later (T2), which in turn predicted an increase in sleep problems 3 years later (T3). Moderation analyses indicated that a higher level of emotional insecurity was a vulnerability factor for sleep problems in the context of greater marital aggression. Findings add to this emerging literature and illustrate the importance of considering sleep in the family context.