Background: Around the world, international migration and growing economic inequality have contributed to heightened perceptions of intergroup threat (i.e., feeling that people outside of one's social group are hostile to their physical or emotional well-being). Exposures related to intergroup threat, like negative intergroup contact, are inherently stressful and may contribute to higher levels of psychological distress in the population. This longitudinal study investigated whether maternal experiences of negative intergroup contact are related to poor mental health outcomes among ethnically diverse children in The Netherlands. Methods: Data are from 4025 mother-child pairs in the Generation R Study, a multi-ethnic Dutch birth cohort initiated in 2005. Mothers’ experiences of negative intergroup contact were assessed during pregnancy. Child mental health was indexed by problem behavior reported by parents and teachers using the Child Behavior Checklist. Linear mixed-effects models tested longitudinal associations of maternal-reported negative intergroup contact with child problem behavior reported by mothers at ages 3, 5, and 9 years, considering a range of potential confounders. Sensitivity analyses examined whether results were replicated using child data from other informants. Results: In fully adjusted models, higher levels of negative intergroup contact were associated with more problem behavior averaged across childhood for both non-Dutch (standardized B = 0.10, 95% CI = 0.05, 0.14) and Dutch children (standardized B = 0.12, 95% CI = 0.08, 0.15). Sensitivity analyses with data from other informants largely supported primary findings. Conclusions: Comparable adverse intergenerational effects on mental health were observed among both ethnic minority and majority children whose mothers experienced negative intergroup contact. These findings suggest that ethnically divisive social contexts may confer widespread risks, regardless of a child's ethnic background. To our knowledge, this study is the first to ...