The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) improves health for young children with low household incomes, but it is underutilized after infancy due to program complexity and lower perceived value of benefits for participants aged 1 to 4 years. Increasing participants’ retention in WIC could be an important strategy for improving the health of young children. This study aimed to evaluate whether policies making WIC easier to use and increasing benefit value were associated with increased retention of participants postinfancy. This repeated cross-sectional experiment used interrupted time series analysis of Massachusetts participants in WIC younger than 4 years enrolled between January 2017 and December 2022. Analyses were conducted in between June 2024 and April 2025. Two policy changes were examined: (1) the introduction of remote WIC services (March 2020) and (2) an increased cash-value benefit for fruits and vegetables, or cash value benefit (June 2021). There were 238 482 WIC-participating children across the study period. In the baseline year (105 782 children), the mean (SD) age was 17.0 (14.0) months, half the sample were female (52 505 [50%]). After remote services were implemented, a previously downward monthly trend in retention reversed, steadily increasing each month afterwards, by 1.04 percentage points (pp) (95% CI, 0.48-1.60 pp) for children aged 12 to 23 months, 1.47 pp (95% CI, 1.06-1.87 pp) for children aged 24 to 35 months, and 1.25 pp (95% CI, 0.79-1.72 pp) for children aged 36 to 47 months. The increased cash value benefit (June 2021) was not associated with changes in retention trends overall, but was associated with immediate increases in the likelihood of retention plus benefit usage among children aged 12 to 23 months and 24 to 35 months. In this repeated cross-sectional study, making remote WIC services available was associated with more children staying enrolled. Policy efforts to make remote service options permanent may support WIC utilization.