Offender and offence characteristics associated with the onset of child sexual abuse in adolescence and adulthood were examined in a sample of males adjudicated for sexual offences. Predictors of adolescent- and adult-onset abuse reinforce that adolescents and adults, for the most part, are two distinct offender populations who may be motivated to sexually abuse for different reasons and who are influenced by opportunity structures, constraints and experiences that characterise these developmental stages. Findings support tailored prevention efforts for adolescents and adults. Emphasis should be placed on primary and secondary prevention efforts that are currently less developed in Australia, compared to tertiary responses.