According to family systems theory, all family subsystems influence each other and are interdependent. This study examines the links among different parental discipline dimensions, family communication, and sibling conflict resolution. We administered the Dimensions of Discipline Inventory, The Family Communication Scale, and the Revised Conflict Tactics Scales—Sibling Version to a sample of 320 Portuguese adolescents. The results show that punitive discipline by mothers and fathers were associated with lower levels of family communication but with higher levels of psychological aggression toward siblings. Family communication played a different role for mother and fathers in the link between parents’ psychological aggression and corporal punishment and negotiation with siblings. These findings have implications for clinical interventions that may reduce sibling conflict.