For this functional magnetic resonance imaging (fMRI) study, we assessed the impact of early social experiences on the social regulation of neural threat responding in a sample of 22 individuals that have been followed for over a decade. At 13 years old, a multidimensional measure of neighborhood quality was derived from parental reports. Three measures of neighborhood quality were used to estimate social capital—the level of trust, reciprocity, cooperation, and shared resources within a community. At 16 years old, an observational measure of maternal emotional support behavior was derived from a mother/child social interaction task. At 24 years old, participants were asked to visit our neuroimaging facility with an opposite-sex platonic friend. During their MRI visit, participants were subjected to the threat of electric shock while holding their friend’s hand, the hand of an anonymous opposite-sex experimenter, or no hand at all. Higher adolescent maternal support corresponded with less threat-related activation during friend handholding, but not during the stranger or alone conditions, in the bilateral orbitofrontal cortex, inferior frontal gyrus and left insula. Higher neighborhood social capital corresponded with less threat-related activation during friend hand-holding in the superior frontal gyrus, supplementary motor cortex, insula, putamen and thalamus; but low childhood capital corresponded with less threat-related activation during stranger handholding in the same regions. Exploratory analyses suggest this latter result is due to increased threat responsiveness during stranger handholding among low social capital individuals, even during safety cues. Overall, early maternal support behavior and high neighborhood quality may potentiate soothing by relational partners, and low neighborhood quality may decrease the overall regulatory impact of access to social resources in adulthood.