Socioeconomic disadvantage during childhood is associated with a myriad of negative adult outcomes. One mechanism through which disadvantage undermines positive outcomes may be by disrupting the development of self-control. The goal of the present study was to examine pathways from three key indicators of socioeconomic disadvantage - low family income, low maternal education, and neighborhood poverty - to neural and behavioral measures of response inhibition. We utilized data from a representative cohort of 215 twins (ages 7-18 years, 70% male) oversampled for exposure to disadvantage, who participated in the Michigan Twins Neurogenetics Study (MTwiNS), a study within the Michigan State University Twin Registry (MSUTR). Our child-friendly Go/No-Go task activated the bilateral inferior frontal gyrus (IFG), and activation during this task predicted behavioral inhibition performance, extending prior work on adults to youth. Critically, we also found that neighborhood poverty, assessed via geocoding, but not family income or maternal education, was associated with IFG activation, a finding that we replicated in an independent sample of disadvantaged youth. Further, we found that neighborhood poverty predicted response inhibition performance via its effect on IFG activation. These results provide the first mechanistic evidence that disadvantaged contexts may undermine self-control via their effect on the brain. The broader neighborhood, beyond familial contexts, may be critically important for this association, suggesting that contexts beyond the home have profound effects on the developing brain and behaviors critical for future health, wealth, and wellbeing.