Individuals with CHD are at increased risk of poor mental well-being. Dietary intake of EPA and DHA, the main n-3 fatty acids from fish, may be beneficial to mental well-being. We examined the association of EPA+DHA and fish intake with mental well-being in 644 participants, aged 60–80 years, with a history of myocardial infarction. Habitual food intake was assessed with a 203-item FFQ. Depressive symptoms were assessed with the self-report geriatric depression scale, and dispositional optimism was assessed with the revised life orientation test (LOT-R) and a four-item questionnaire (4Q). In Cox-regression models modified for cross-sectional analyses, we adjusted for sex, age, energy intake, BMI, family history of depression, education, marital status, smoking, physical activity and intake of saturated fat, alcohol and fibre. Compared with the lower tertile, subjects in the higher tertile of EPA+DHA intake had a lower prevalence of depressive symptoms, but this association was not statistically significant (prevalence ratio (PR) 0·78; 95 % CI 0·50, 1·22, P-trend 0·27). The higher tertile of EPA+DHA intake was positively associated with dispositional optimism measured with the 4Q (PR 0·69; 95 % CI 0·46, 1·03, P-trend 0·05), but not according to the LOT-R. Fish intake was not related to either depressive symptoms or dispositional optimism. In conclusion, intake of EPA+DHA was positively associated with dispositional optimism assessed with the 4Q, but not with optimism assessed with the LOT-R or with depressive symptoms.