The increasing elderly population presents major healthcare challenges worldwide, with elderly women being particularly vulnerable due to biological and cultural factors. Educational interventions can improve health-promoting behaviors and mental health in older adults, yet limited evidence exists for culturally-adapted interventions in developing countries like Iran. This randomized clinical trial evaluated an educational intervention’s effect on mental health and health-promoting behaviors in 140 elderly women aged 60 years and older in southern Iran. Participants were randomly assigned to intervention (n = 70) and control (n = 70) groups with no sample attrition. The intervention group received seven 60-minute educational sessions on acceptance of age-related changes, physical activity, interpersonal relationships, stress management, positive thinking, and spiritual growth. Data were collected using demographic questionnaires, Health-Promoting Lifestyle Profile II, and General Health Questionnaire-28, then analyzed using IBM SPSS Statistics version 27 with independent and paired t-tests and Cohen’s effect size indices. Baseline comparisons showed no significant group differences (p > 0.05). One-month post-intervention, the intervention group demonstrated significant improvements in all health-promoting behavior dimensions and mental health indices compared to controls (p < 0.001 for all comparisons), with effect sizes indicating 98–100% of intervention participants outperforming controls. This culturally-adapted multidimensional educational intervention significantly improved mental health and health-promoting behaviors in elderly Iranian women.