Some developmental models of childhood aggression deny any influence of socioeconomic status (SES), while others stress a more central role. We argue that greater attention to persistent material hardship (i.e., inability to provide for basic needs) may enhance the centrality of SES in developmental approaches. We analyze a longitudinal sample of children in the Fragile Families and Child Well-Being Study, and examine whether persistent material hardship shapes patterns of childhood aggression. We find that while the majority of children are insulated, some experience multiple, enduring hardships. More importantly, experiencing a single, persistent hardship during the period of childhood increases the likelihood of aggression by 4.8% among males and 6.4% among females, a magnitude that is comparable to the influence of impulsivity. Findings warrant greater attention to the consequences of material hardship in theoretical models and life course research that goes beyond the traditionally-examined indicators of SES.