Purpose: To examine the impact of parental criminal offending, both paternal and maternal, on offspring aggression at age 5 years, while also considering key risk factors, including parental mental illness, child’s sex, and socioeconomic disadvantage. Methods: The sample comprised 69,116 children, with linked parental information, from the New South Wales Child Development Study, a population-based multi-agency, multi-generational record linkage study that combines information from a teacher-reported cross-sectional survey of early childhood development at age 5 years (the 2009 Australian Early Development Census; AEDC) with data obtained via administrative records from multiple sources (e.g., health, crime, education, and welfare). Hierarchical logistic regression analyses were conducted to determine the effects of maternal and paternal criminal court appearances (frequency and type of offending), and mental health service contacts, on offspring aggression measured in the AEDC. Results: Having a parent with a history of offending was significantly associated with high levels of offspring aggression in early childhood. The strength of association was greatest when parents were involved in frequent (≥6 offences: adjusted odds ratio [aOR] range = 1.55–1.73) and violent (aOR range = 1.49–1.63) offending. Both maternal and paternal offending remained significant predictors of offspring aggression after accounting for parental mental illness, and associations were similar in magnitude for maternal and paternal offending histories. Conclusions: Parental history of severe criminal offending increased the risk of high levels of aggression in offspring during early childhood, highlighting the need for intervention with families during this key developmental period.