Many children in immigrant households endure unique stressors shaped by national, state, and local immigration policies and enforcement activity in the United States. Qualitative studies find that during times of heightened immigration enforcement, children as young as 3 years of age show signs of behavioral distress related to national anti-immigrant sentiment and the possibility of losing a parent. Using multiple sources of data from 168 racially and ethnically diverse families of children in pre-Kindergarten, the present study examined variability in perceived levels of immigration enforcement threat by parental immigrant status and ethnicity. This study examined associations between immigration enforcement threat and child mental health, self-regulation, and executive functioning and whether parent immigrant status or child gender moderates these associations. We found substantial variability in perceived immigration threat, with immigrant parents and Latinx parents reporting significantly greater levels of immigration threat compared to nonimmigrant parents and non-Latinx parents. Immigration enforcement threat was associated with greater child separation anxiety and overanxious behaviors, and lower self-regulation among boys and girls and among children of immigrant and U.S.-born parents. In contrast to our hypothesis, immigration enforcement threat was associated with higher self-regulation according to independent assessor ratings. Educators and healthcare providers working with young children from immigrant and Latinx households should be aware of the disproportionate stress experienced by immigrant and Latinx families due to a xenophobic sociopolitical climate marked by heightened immigration enforcement threat and racist, anti-immigrant rhetoric. Public Policy Relevance Statement: Findings indicate that immigrant and Latinx families experience disproportionate worry related to the racialized sociopolitical climate, changes in immigration policies, national anti-immigrant rhetoric and increased immigration enforcement activity in the U.S. interior. Children in pre-Kindergarten may have unmet mental health needs given the manifestation of immigration-related fears as internalizing behaviors, rather than externalizing behaviors, which may go undetected in schools. [ABSTRACT FROM AUTHOR]