This study compared the moral development of solo juvenile male sex offenders (n = 20) and juvenile male non-offenders (n = 76), aged 13-19 years, from lower socioeconomic and educational backgrounds. The Moral Orientation Measure (MOM) was used to assess punishment- and victim-based moral orientation in sexual and non-sexual situations. Moral judgement was assessed with the Sociomoral Reflection Measure-Short Form (SRM-SF), with questions added on sexual offending and the offender's own victim(s). Offenders did not differ from non-offenders in victim-based orientation, but they showed weaker punishment-based orientation in sexual and non-sexual situations. No differences in moral judgement were found. However, lower stages of moral judgement were observed when the offenders' own victim was involved, confirming specific moral deficits in solo juvenile sex offenders. Delay in moral judgement proved to be associated with cognitive distortions. It was concluded that the treatment of solo juvenile sex offenders should challenge own victim-related cognitive distortions. (Contains 1 table.)