The early development of threat perception in infancy might be dependent on caregiver context, but this link has not yet been studied in human infants. This study examined the emergence of the young infant's response to threat in the context of variations in caregiving behavior. Eighty infant-caregiver dyads (39 female infants, all of western European descent) visited the laboratory when the infant was 5 months old. Each dyad completed a free-play task, from which we coded for the mother's level of engagement: the amount of talking, close proximity, positive affect, and attention directed toward the infant. When the infant was 7 months old, they came back to the laboratory and we used functional near infrared spectroscopy and eye tracking to measure infants’ neural and attentional responses to threatening angry faces. In response to threat, infants of more-engaged mothers showed increased brain responses in the left dorsolateral prefrontal cortex—a brain region associated with emotion regulation and cognitive control among adults—and reduced attentional avoidance. These results point to a role for caregiver behavioral context in the early development of brain systems involved in human threat responding.