Research Findings: Marginal food security is less studied relative to food insecurity but may also have adverse effects on family outcomes. The present study examined whether parental stress mediated the relationship between marginal food security (MFS) and preschool-aged children's observed self-regulation at three early education centers located in two urban cities in a Midwestern state. Primary caregivers (81.3% mothers) completed an adapted version of the Parenting Stress Index-Short Form and a two-question screener from the USDA Annual Food Security Survey. Children's aged 37-70 months, M= 54, SD = 6.46; 57% boys) self-regulation skills were directly assessed. Approximately one-third (39.75%) of the present sample were considered MFS, as they reported being "worried that food would not last" in the past 12 months. MFS families had significantly higher levels of parental stress than food secure families. Additionally, MFS indirectly affects children's observed self-regulation skills through parental stress, even after controlling for the effect of child age, sex, and family structure. Practice or Policy: Implications of this finding for early intervention and food support programs are discussed.