Surviving a myocardial infarction (MI) can be a stressful event entailing challenges in daily life during the recovery period. Experiencing fatigue symptoms post-MI has been described as bothersome and occurs in nearly half of patients four months and two years after MI. The aetiology of fatigue disorder is unclear, but research has shown that fatigue plays an important role in the relationship between stress and perceived poor health. Previous findings indicate that having access to an easily administered stress measurement is worthwhile both in the clinic and in research. The single-item measure of stress symptoms has not been validated in persons treated for MI. The aim was to validate the single-item measure of stress symptoms and to explore its association with fatigue in a sample of persons treated for MI. Methods: 142 respondents completed the questionnaires of the Multidimensional Fatigue Inventory-20, the single-item measure of stress symptoms and the Perceived Stress Scale-10 (PPS-10) two months post-MI. Correlation analysis and t-tests were used to validate the single-item stress measure and its association with post-MI fatigue. Results: The convergent validity of the single-item measure of stress symptoms was confirmed. In analyses of relations between stress and fatigue, it was found that the single-item stress measure was strongly associated with both the global fatigue score and all four fatigue dimension scores (general, physical and mental fatigue as well as reduced activity). Conclusion: The single-item measure of stress symptoms was found to be a valid measure of post-MI stress. Also, the measure was useful in assessing associations between stress and fatigue and could therefore indicate that U. Fredriksson-Larsson et al. 346post-MI fatigue experiences should be further explored in full using multidimensional fatigue assessment.