Research in developmental psychology has robustly documented positive associations between parent-child attachment security and the child's self-regulation (SR). This study of 102 community mothers, fathers, and infants contributes to that research by examining the role of attachment security, observed at 15 months using Attachment Q-Set (AQS, Waters, 1987), as a predictor of two distinct aspects of SR at 67 months: Executive functioning (SR-EF), observed in abstract Stroop-like tasks (Day/Night, Snow/Grass, and Tapping), and parent-related (SR-PR) self-regulated behavior, observed within the context of the parent-child relationship in response to the mother’s (SR-MR) and father’s (SR-FR) requests and prohibitions. We also examined child anger proneness, observed at 7 months, as a moderator of those associations. In both mother- and father-child dyads, child security predicted SR-EF: More secure children performed better in executive functioning tasks. In mother-child dyads, security also predicted SR-MR, but the effect was qualified by the interaction of security and anger proneness, such that the effect was significant only for highly anger-prone children. The effect reflected differential susceptibility: Compared to lower-anger peers, highly anger-prone children developed worse SR-MR if their security was low, but better SR-MR if their security was high. The findings highlight the benefits of a nuanced approach to self-regulation, considering child individuality as interacting with security, and examining processes in both mother- and father-child dyads.