The construct of moral disengagement has increasingly been used by researchers to account for the asymmetry between children's moral reasoning and their moral behavior. According to this theory, moral disengagement occurs most aptly when children are motivated to violate their moral beliefs, such as when they hold antisocial goals during social conflict. In line with this, the current study examined whether moral disengagement would mediate the associations among children's antisocial and prosocial goals and aggressive behavior, both concurrently and over time. Specifically, cross-sectional and longitudinal data from 379 children were examined during and across their fourth-, fifth-, and sixth-grade school years. Findings provide evidence that moral disengagement mediates the concurrent association between antisocial goals and higher levels of aggressive behavior, as well as the concurrent association between prosocial goals and lower levels of aggressive behavior. Further, moral disengagement emerged as a significant mediator of the longitudinal association between prosocial goals and lower rates of aggressive behavior toward peers across the span of middle childhood. Finally, moral disengagement also emerged as a potential mechanism in the continued endorsement of relationship maintenance goals over time. Findings are discussed in terms of theoretical and practical implications.