The intergenerational transmission of criminality is well established. However, few intergenerational studies in Australia have examined the link between parents’ offending and their children’s behaviour. Even fewer have used large enough samples to examine serious maternal offending. This study uses a sample of over 21,000 Australian children and their parents to determine the prevalence and co-occurrence of offending among mothers and fathers, and the relationship between parental offending and children’s conduct problems at age 11. The study found that parental offending increases a child’s likelihood of conduct problems, and the offending most strongly associated with child conduct problems is maternal violent offending. It also found that the intergenerational transmission of antisocial behaviour begins early, highlighting the importance of intervention for at-risk children and programs targeted at mothers as well as fathers.