<p>Despite growing research on the youth crime decline, there has been limited analysis of how these trends have influenced offending trajectories in cohorts born after the mid-1990s. This study aimed to examine changes in offending trajectories among Australian adolescents with a proven offence aged 10–16&#xa0;years across 12 consecutive birth cohorts (1995 to 2006), in Queensland, Australia. Findings indicate notable polarisation of youth offending participation and frequency trends, with a 44% decrease in the number of adolescents with a proven offence from the oldest to the youngest cohort, but significant increases in high frequency and violent offending in recent cohorts of justice-involved adolescents. Additionally, despite declines in offending participation, First Nations adolescents have become more over-represented in the youth justice system, due to steeper declines in offending participation for non-First Nations adolescents. Latent class growth analysis identified three types of offending trajectories across the birth cohorts. Multinomial logistic regression indicated that recent cohorts of justice-involved adolescents were significantly more likely to display moderate or chronic offending trajectories, compared to low-level offending. Findings suggest that while criminogenic risk has reduced across the majority of adolescents in recent birth cohorts, for a subset of adolescents it has also increased. Theoretical and policy implications are explored.</p>