["Family Relations, EarlyView. ", "\nABSTRACT\n\nObjective\nTo examine whether mentalization mediates the association between self‐differentiation and dyadic adjustment in couples using a dyadic model.\n\n\nBackground\nSelf‐differentiation (balancing intimacy and autonomy) and mentalization (understanding one's own and others' mental states) are both linked to relationship functioning, yet their combined contribution to couple adjustment has rarely been tested at the dyadic level.\n\n\nMethod\nOne hundred fifty‐eight heterosexual couples from Turkey completed self‐report measures of self‐differentiation, mentalization, and dyadic adjustment. An actor–partner interdependence mediation model (APIMeM) was estimated to examine actor and partner pathways simultaneously.\n\n\nResults\nHigher self‐differentiation was associated with greater mentalization for both women and men, and greater mentalization was associated with better dyadic adjustment. Modest but significant partner effects indicated that one partner's mentalization was positively associated with the other partner's dyadic adjustment. Cross‐partner associations between self‐differentiation and the partner's mentalization were not significant.\n\n\nConclusion\nSelf‐differentiation was indirectly linked to dyadic adjustment primarily through partners' own mentalization, alongside modest between‐partner associations of mentalization with adjustment.\n\n\nImplications\nCouple interventions that support both differentiation processes and mentalizing may strengthen dyadic adjustment by targeting individual and relational regulatory processes.\n\n"]