Past studies have shown that aggressive children exhibit rigid (rather than flexible) parent–child interactions; these rigid repertoires may provide the context through which children fail to acquire emotion-regulation skills. Difficulties in regulating emotion are associated with minimal activity in dorsal systems in the cerebral cortex, for example, the anterior cingulate cortex. The current study aimed to integrate parent–child and neurocognitive indices of emotion regulation and examine their associations for the first time. Sixty children (8–12 years old) referred for treatment for aggression underwent two assessments. Brain processes related to emotion regulation were assessed using dense-array EEG with a computerized go/no-go task. The N2 amplitudes thought to tap inhibitory control were recorded, and a source analysis was conducted. In the second assessment, parents and children were videotaped while trying to solve a conflict topic. State space grids were used to derive two dynamic flexibility parameters from the coded videotapes: (a) the number of transitions between emotional states and (b) the dispersion of emotional states, based on proportional durations in each state. The regression results showed that flexibility measures were not related to N2 amplitudes. However, flexibility measures were significantly associated with the ratio of dorsal to ventral source activation: for transitions, ΔR2 = .27, F (1, 34) = 13.13, p = .001; for dispersion, ΔR2 = .29, F (1, 35) = 14.76, p < .001. Thus, in support of our main hypothesis, greater dyadic flexibility was associated with a higher ratio of dorsomedial to ventral activation, suggesting that children with more flexible parent–child interactions are able to recruit relatively more dorsomedial activity in challenging situations.