The association between paternal involvement in therapy, adolescent outcomes and maternal depression was examined within the context of Multisystemic Therapy (MST), an empirically supported, family- and community-based treatment for antisocial adolescents. Ninety-nine families were recruited from five mental health agencies providing MST. We compared families with paternal involvement in therapy (PIT) to families with no paternal involvement in therapy (NPIT) in pre-post change in adolescents' externalizing and internalizing behaviours and also in maternal depression. There was a significant reduction in both groups in externalizing and internalizing behaviours. However, the magnitude of improvement was significantly greater for the PIT families. Both groups saw a significant reduction in maternal depression but no significant group differences were found. Results suggest that if possible, paternal figures should be encouraged to actively participate in therapy, as adolescents outcomes are enhanced when mothers and paternal figures participate in MST together. (Contains 2 tables.)