Background: There is a view that young people presenting with an animal cruelty and firesetting combination represent a uniquely risky group, but prior work has relied on samples with insufficient power. Research question: What is the prevalence of the co-occurrence of animal cruelty and firesetting behaviour among young delinquents? What other features correlate with this?. Methods: We measured the prevalence of animal cruelty and firesetting among 292,649 juvenile offenders and used rare events logistic regression to examine demographic, criminal, mental health and family histories as correlates. Results: The prevalence of animal cruelty was 0.59%, accounting for 1732 young people, and of firesetting 1.56% (n = 4553). The co-occurrence of these behaviours was rare: 0.17% (n = 498), but approximately twice that expected by chance based on the prevalence of each behaviour individually (0.59% × 1.56% = 0.009%). Rates were higher in males, older youths and Whites. Among historical variables, criminal history was the strongest correlate, followed by mental health problems, then familial and individual indicators. Conclusions: As only male gender and being a victim of sexual abuse increased the odds of evidencing both animal cruelty and firesetting behaviour substantially above the odds for each behaviour individually, there thus appears to be little that is unique to the co-occurrence. Our findings suggest that sensitivity to the occurrence of each is the best way forward, with rather familiar assessments and interventions offering some hope of reducing these seriously damaging behaviours.