This article reports a test of multisystemic predictors of therapeutic engagement (TE) with adolescent sexual offenders (ASOs), and an evaluation of clinical efforts to improve TE with this client group. First, clinicians rated their TE with 105 Australian court-referred male ASOs (M?=?15.53 years; SD?=?1.30 years), who participated in treatment between 2001 and 2005. For this cohort, correlation analysis showed impulsivity/antisociality, negative peer relationships, and indigenous race to be associated with poorer TE. Multiple regression analysis identified impulsivity/antisociality and indigenous race as significant unique predictors. Clinical efforts subsequently focused on improving TE, particularly with higher-antisocial youth and with indigenous youth and their families. Clinicians then rated TE with a second, independent cohort of 54 court-referred male ASOs (M?=?15.44 years; SD?=?1.22 years), who participated in the modified treatment between 2006 and 2009. A two-way ANCOVA, controlling for impulsivity/antisociality, indicated significant improvements in TE for both indigenous and non-indigenous ASOs. Despite these general improvements, indigenous ASOs remained comparatively less engaged than their non-indigenous counterparts.