Background <p>Balancing work and family demands is a significant challenge for dual-earner couples, often undermining relationship satisfaction. While core self-evaluation is a well-established predictor of work-related well-being, its interpersonal effects on romantic relationships remain underexplored. Guided by conservation of resources and spillover-crossover theories, this study investigates the dyadic association between core self-evaluation and relationship satisfaction and examines the parallel mediating roles of work-to-family and family-to-work conflict.</p> Methods <p>Survey data from 271 Croatian dual-earner couples were analysed using an actor-partner interdependence mediation model. Both partners self-reported on the Core Self-Evaluations Scale, the Work-Family Conflict Scale, and the Perceived Relationship Quality Components Questionnaire.</p> Results <p>The analysis indicated significant positive actor effects: individuals' core self-evaluation was associated with their own higher relationship satisfaction. For women, this association was fully mediated by their own lower work-to-family conflict. A significant indirect partner effect also emerged: men’s core self-evaluation was associated with higher relationship satisfaction in their partners via the men’s lower work-to-family conflict. Family-to-work conflict was not a significant mediator, and no significant gender differences were found in the overall strength of the actor or partner effects.</p> Conclusions <p>The study underscores core self-evaluation may function as a psychological resource for relationship satisfaction in dual-earner couples, operating through the mitigation of work-family conflict. The findings highlight distinct gendered pathways, suggesting processes of spillover for women and crossover from men to women. Interventions aimed at strengthening personal resources and managing work-domain stressors may enhance both individual and relational well-being.</p>