Objectives. To examine the effects of childhood participation in the Supplemental Nutrition Assistance Program (SNAP) and the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) on adult food security in the United States. Methods. We used data from the 1984 to 2019 waves of the Panel Study of Income Dynamics to follow a balanced panel of 1406 individuals from birth through ages 20 to 36 years. We measured food insecurity from 1999 to 2003 and 2015 to 2019 among those who resided in low-income households during childhood. Results. Twenty-eight percent of individuals who resided in low-income households during childhood exhibited improved food security status from childhood to adulthood. Those who participated in SNAP and WIC during childhood had 4.16-fold higher odds (95% confidence interval [CI] = 1.91, 9.03) of being more food secure than those who were eligible for but did not receive SNAP or WIC, and those who participated in SNAP alone had 3.28-fold higher odds (95% CI = 1.56, 6.88). Conclusions. Participation in social safety net programs such as SNAP and WIC during childhood helps to improve food security across the life course. Our findings add evidence regarding the long-term benefits of participation in SNAP and WIC during childhood. (Am J Public Health. 2022;112(10):1498-1506. https://doi.org/10.2105/AJPH.2022.306967).