BACKGROUND: Previous studies have suggested a link between diet and mental health. However, there is a lack of evidence regarding the association between emerging diets such as the EAT-Lancet reference diet (ELD) and the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, and mental health in different societies. This study aimed to determine the association between adherence to ELD and MIND diets and the risk of depression, anxiety, and stress. METHODS: This research involved 4579 participants from the PERSIAN Organizational Cohort Study in Mashhad (POCM). To assess dietary intake, a comprehensive 118-item semi-quantitative food frequency questionnaire (FFQ) was employed. The Planetary Health Diet Index (PHDI) was used to assess adherence to the ELD. Mental health status was evaluated using the Depression, Anxiety, and Stress Scale-21 items (DASS-21) questionnaire. Binary logistic regression was utilized to examine the relationship between these scores and mental health indicators. RESULTS: In the adjusted model, the highest quartile of PHDI showed a 35% reduced risk of depression compared to those in the lowest quartile (OR: 0.653, 95% CI: 0.483-0.883; P = 0.008). However, compared to the reference quartile, participants in the highest quartile of MIND diet exhibited significantly lower risks of depression (OR: 0.611, 95% CI: 0.447-0.836; P = 0.005), anxiety (OR: 0.559, 95% CI: 0.418-0.746; P < 0.001), and stress (OR: 0.629, 95% CI: 0.419-0.944; P = 0.008). CONCLUSIONS: The ELD and MIND diet were both associated with reduced odds of depression. Additionally, MIND diet was associated with decreased likelihood of anxiety and stress. However, no connection was observed between ELD and anxiety or stress. Further large-scale interventions are required to confirm these findings.