Previous research has documented socioeconomic-related disparities in children's working memory; however, the putative proximal caregiving mechanisms that underlie these effects are less known. The present study sought to examine whether the effects of early family socioeconomic status on children's working memory were mediated through experiences of caregiving, specifically maternal harsh discipline and responsiveness. Utilizing a psychobiological framework of parenting, the present study also tested whether maternal working memory moderated the initial paths between the family socioeconomic context and maternal harsh discipline and responsiveness in the mediation model. The sample included 185 socioeconomically diverse mother-child dyads assessed when children were 3.5 and 5 years old. Results demonstrated that maternal harsh discipline was a unique mediator of the relation between early experiences of family socioeconomic adversity and lower working memory outcomes in children. Individual differences in maternal working memory emerged as a potent individual difference factor that specifically moderated the mediating influence of harsh discipline within low socioeconomic contexts. The findings have implications for early risk processes underlying deficits in child working memory outcomes and potential targets for parent-child interventions.