Mental health problems during adolescence constitute a major public health concern today for both families and stakeholders. Accordingly, different family-based interventions have emerged as an effective treatment for adolescents with certain disorders. Specifically, there is evidence of the effectiveness of concrete approaches of systemic family therapy on the symptoms of adolescents and family functioning in general. However, few studies have examined the effectiveness of other relevant approaches, such as structural and strategic family therapy, incorporating parent–child or parental dyadic measurement. The purpose of this study was to test the effectiveness of a structural–strategic family therapy with adolescents involved in mental health services and their families. For this purpose, 41 parents and adolescents who participated in this treatment were interviewed at pre-test and post-test, providing information on adolescent behavior problems, parental sense of competence, parental practices, parenting alliance, and family functioning. Regardless of participants’ gender, adolescents exhibited fewer internalizing and externalizing problems after the treatment. Parents reported higher family cohesion, higher satisfaction and perceived efficacy as a parent, and healthier parental practices (less authoritarian and permissive practices, as well as more authoritative ones). An interaction effect between parenting alliance and gender was found, with more favorable results for the mothers. In conclusion, this paper provides evidence of the usefulness of structural–strategic family therapy for improving family, dyadic, and individual facets in families with adolescents exhibiting mental health problems.