<p>Understanding mechanisms of change in parenting interventions for early-onset conduct problems is crucial for improving treatment effectiveness. This study is the first to explicitly test marital quality as a mediator of change in reducing parental distress among families with young children with conduct problems. Using data from a randomized controlled trial (N = 209 parents, including both mothers and fathers) of the <i>Hitkashrut</i> program, we tested whether improvements in marital quality mediated intervention effects on parental distress, defined as parental stress and sense of helplessness. Structural equation modeling revealed that marital quality significantly mediated the intervention's impact on parental distress, while an alternative model testing parental distress as mediator yielded non-significant results. These findings advance understanding of how interventions achieve their effects through family subsystems and suggest that marital quality enhancement may be an important component for maximizing intervention impact.</p>