: Past research indicates females prefer the use of indirect over direct forms of aggression, whereas the opposite pattern has been found for males. We investigated a specific form of aggression: parental alienating behaviors. Parents who alienate their children from another parent utilize both direct and indirect forms of aggression. We examined whether there are gender differences in the use of these behaviors by analyzing data from two samples: interviews with parents who have been the target of parental alienating behaviors, and family law appellate court rulings in which parental alienation was found. In both studies, mothers used significantly more indirect than direct parental alienating strategies. In contrast, fathers tended to use similar levels of both indirect and direct parental alienating strategies. Further, fathers did not use more direct forms of this type of aggression than mothers. Better standards of practice for the assessment of parental alienation must be developed to prevent misdiagnoses and gender biases.