Aggression among youth is a public health problem that is often studied in the context of how youth interpret social information. Social cognitive factors, especially hostile attribution biases, have been identified as risk factors for the development of youth aggression, particularly across the transition to middle school. Parental behaviors, including parental aggression to children in the form of corporal punishment and other aggressive behavior, have also been linked to aggressive behavior in children at these ages. Despite the important role played by these two risk factors, the connection between the two has not been fully studied in the literature. This study examined the link between parental aggression and children’s hostile attributions longitudinally among a diverse sample of 123 boys as they entered middle school. Results support acceptance of a model in which parental aggression to children prior to entering middle school predicted children’s hostile attributions after the transition to middle school above and beyond that which was predicted by previous levels of hostile attributions. As expected, hostile attributions also predicted change in parent- and teacher-rated child aggression. These findings provide important evidence of the role that parental behavior plays in youth social cognition at this critical age, which has implications for understanding the development of aggressive behavior.