The lifetime costs of offenders to the criminal justice system provide useful information to support implementation of innovative frameworks such as justice reinvestment and payment by outcome, as well as helping to assess the effectiveness of targeted prevention programs. However, few Australian studies have explored the longitudinal costs of offenders and no research has explored whether criminal justice system costs differ based on Indigenous status. This study used linked administrative data (contacts individuals born in 1983 and 1984 had with police, courts and corrections in Queensland) to determine how offending develops over the life course and how Indigenous status influences offending trajectories. A narrow costing framework focused on direct criminal justice system costs used in service provision (police, courts, youth justice and corrections) was developed to establish unit cost estimates based on critical cost drivers (eg whether diverted, offence type, trials and sanction type). These cost estimates were modelled to assess the costs of individuals on different trajectories. Findings identified over half (53%) of the Indigenous population and 16 percent of the non-Indigenous population had moderate to chronic trajectories of offending. Because of the high levels of recontact, Indigenous offenders were on average more costly. These findings emphasise the need for innovative approaches such as justice reinvestment/payment-by outcome to reduce Indigenous over-representation.