The present study assessed two theory-driven mediators of the effects of a family group cognitive-behavioral (FGCB) preventive intervention for youth of parents with a history of major depressive disorder (MDD) or dysthymia on long-term youth psychopathology symptoms and diagnoses. Sample included 180 parents ( Changes in youth SCC skills (e.g., acceptance, reappraisal) after the intervention mediated the effects of the FGCB program on changes in youth internalizing and externalizing symptoms at 18- and 24-month follow-ups. Effects for changes in positive parenting behaviors as a mediator were more limited. SCC skills were further shown to mediate the effects of the FGCB intervention on MDD diagnoses from 12 to 24 months. This study provides clear and strong evidence that changes in youth SCC skills mediated the long-term effects of preventive intervention for families of depressed parents. (PsycInfo Database Record (c) 2025 APA, all rights reserved).