The association between experienced racial discrimination and poor health is now well documented, particularly among adult populations. However, longitudinal studies of the association between racism and child health are limited, and evidence on how racial discrimination experienced by members of children’s immediate environment impact on child development, and the mechanisms by which this occurs, is scarce. We examined the longitudinal association between maternal, family, and area-level experiences of racial discrimination, and children’s socioemotional development. We proposed that exposure to racial discrimination would be detrimental to children’s socioemotional development via two mother-centred stress pathways: a worsening in maternal mental health, and an increase in harsh parenting practices. Data on ethnic minority mothers and their children were drawn from waves 3 to 5 (2006-2012) of the UK Millennium Cohort Study. Results of longitudinal path analyses show a strong association between maternal and family experiences of racial discrimination in wave 3, and a worsening in mother’s mental health in wave 4. Maternal and family experiences of racial discrimination at wave 3 had an indirect effect on children’s socioemotional development at wave 5. This occurred mainly via a worsening in mother’s mental health, although some events of racial discrimination experienced by the mother and other family members also impacted negatively on children’s socioemotional development via an increase in harsh parenting practices. We found a direct effect of maternal and family experiences of racial discrimination on children’s socioemotional development. Our findings document the harm of growing up in a racist environment on the socioemotional development of children, and provide some evidence for the role of mother-centred stress mechanisms in linking vicarious exposure to racial discrimination to children’s socioemotional development.