The overall aim of this multi-informant study was to examine pre–post treatment changes, and maintenance at 3-year follow-up, for multiple dimensions of the family context, for a modular intervention that has previously demonstrated significant clinical improvements in child behavior and maintenance of these effects. Family outcomes included parenting practices (i.e., positive parenting, harsh/inconsistent parenting, psychological/physical aggression), parent functioning (i.e., symptoms of psychopathology, self-efficacy), and family functioning (i.e., family adaptability/cohesion, social support, negative life events). The sample comprised 139 families with children ages 6 to11 who participated in a modular treatment protocol for early-onset oppositional-defiant disorder or conduct disorder that has already been associated with improved child behavior outcomes, delivered in a nonrandomized comparison of research clinic and community settings. Improvement from pre- to post-treatment included indicators of maternal psychological distress and negative parenting practices (e.g., corporal punishment, inconsistent discipline, psychological aggression). Psychological aggression significantly increased following treatment termination; corporal punishment continued to decrease during the 3-year follow-up period. Results are discussed in the context of treatment effects in the broader family context and potential needs for continued intervention research and development.