Middle-aged adults face unique challenges—empty nest syndrome, retirement, and physical health decline—that underscore the importance of self-efficacy in fostering psychological resilience and relational well-being. This study examines the relationship between self-efficacy, psychological distress (anxiety and depression), and marital satisfaction in middle-aged adults, with perceived social support as a mediator. Grounded in Bandura’s self-efficacy theory, which posits that social resources amplify self-beliefs’ effects, this cross-sectional study involved 350 married adults aged 40–60 in Tehran, Iran. Participants completed the General Self-Efficacy Scale (GSE), Depression Anxiety Stress Scales (DASS-21), ENRICH Marital Satisfaction Scale, and Multidimensional Scale of Perceived Social Support (MSPSS). Structural equation modeling (SEM) with bootstrapped confidence intervals tested the mediation model. Results showed strong associations between self-efficacy and psychological distress (β = -0.60, p < .001) and marital satisfaction (β = 0.56, p < .001). Perceived social support fully mediated the self-efficacy–psychological distress relationship (β = -0.32, p < .01) and partially mediated the self-efficacy–marital satisfaction link (β = 0.27, p < .01). Self-efficacy thus enhances perceived social support, buffering psychological distress and strengthening marital bonds. As one of the few studies in a collectivist culture, this research highlights how cultural emphasis on social bonds shapes psychological and relational outcomes. Findings advocate for couple-based psychoeducational workshops, delivered by clinicians, to promote self-efficacy and social support, enhancing psychological and marital well-being in midlife.