Anti-immigrant public policies and rhetoric during 2017-19 may have eroded enrollment in safety-net programs, such as the enrollment of children of immigrants in the Supplemental Nutrition Assistance Program (SNAP). At the same time, states' expansion of Medicaid through the Affordable Care Act may have mitigated erosion through coordinated enrollment across safety-net programs, including SNAP and Medicaid. We examined changes in SNAP participation rates by parental immigration status among low-income households in 2015-16 versus 2017-19 for differences by child race and ethnicity or state Medicaid expansion status. Relative to those among citizen children with US-born parents, SNAP participation rates among citizen children from mixed-status families and noncitizen children significantly decreased between 2015-16 and 2017-19, with the magnitude of disparity widening over time. Declines in SNAP participation were sharper for Hispanic and Latino children from mixed-status families, Hispanic and Latino noncitizen children, and noncitizen children residing in nonexpansion states. Findings are consistent with some policy makers' concerns of erosion in SNAP participation. Mechanisms that could be employed to help reverse these trends include policies, outreach strategies, and enrollment processes.