Although a relationship between child maltreatment and juvenile offending has been documented, little is known about the way in which maltreatment affects the timing and frequency of juvenile offending. Recent work on antisocial behaviour and offending in adolescents suggests that young people exposed to negative childhood experiences are more likely to offend earlier in life and more frequently than those who have not been exposed to such risk factors. The purpose of this study is to explore how one childhood risk factor, being maltreatment, influences the age of onset and frequency of juvenile offending. This study used the records of an Australian birth cohort who are now 18 and who came to the attention of the Department of Families (Queensland) about a child maltreatment matter, a juvenile justice matter, or both. Children who were maltreated were more likely to offend than children without official maltreatment records and were also more likely to offend earlier and more frequently that children who had not been maltreated. This research has important implications for understanding the onset of criminal careers and for the allocation of resources into crime prevention interventions and effective responses to maltreatment.