Growing research has documented distinct developmental sequelae in insecure and secure parent–child relationships, supporting a model of early attachment as moderating future developmental processes rather than, or in addition to, a source of direct effects. We explored maladaptive developmental implications of infants’ anger proneness in 102 community families. Anger was assessed in infancy through observations in the Car Seat episode and parents’ ratings. Children's security with parents was assessed in the Strange Situation paradigm at 15 months. At preschool age, child negativity (defiance and negative affect) was observed in interactions with the parent, and at early school age, oppositionality was rated by parents and teachers. Security was unrelated to infant anger; however, it moderated associations between infant anger and future maladaptive outcomes, such that highly angry infants embarked on a negative trajectory in insecure, but not in secure, parent–child dyads. For insecure, but not secure, mother–child dyads, infants’ mother-rated anger predicted negativity at preschool age. For insecure, but not secure, father–child dyads, infants’ anger in the Car Seat predicted father- and teacher-rated oppositional behavior at early school age. Results highlight the developmentally complex nature of the impact of attachment, depending on the relationship with mother versus father, type of measure, and timing of effects.