The purpose of this study was to evaluate the effects of the state Earned Income Tax Credit on food insecurity among economically at-risk U.S. households with children and explore differential effects across sociodemographic groups. The authors used an intent-to-treat causal inference design and household-level data from all 50 U.S. states available from the Current Population Survey. The authors estimated the effect of state variation in Earned Income Tax Credit generosity on food insecurity from 2001 to 2022 among a sample of 153,683 households with children and limited parent educational attainment. Analyses were performed in 2024. Compared with households living in states without a refundable state Earned Income Tax Credit, those living in states with the most generous refundable tax credits experienced significant declines in food insecurity (0.25 percentage point reduction [95% CI= −0.42, −0.09]). In addition, beneficial reductions in food insecurity were observed to be larger for single-headed than for partnered households and for non-Hispanic Black than for non-Hispanic White households. Findings indicate that state legislatures that elected to implement a more generous refundable state Earned Income Tax Credit have also improved childhood food security among households at high risk for economic hardship.