This study identified predictors of anxiety and depression in patients with acute coronary syndrome. Predictors included illness beliefs, fear/threat at the time of the cardiac event, threat reappraisal over time and social support. A total of 97 participants completed questionnaires in hospital and 1- and 6-month follow-up. Perceived threat and fear at the time of the cardiac event predicted affective response at both time points, partly mediated by threat reappraisal. Contemporaneous measures of illness beliefs contributed additional variance, although not always in the predicted direction: high concern and control over the illness were associated with emotional distress. Assessment of patients for risk of negative emotional outcomes of acute coronary syndrome needs to consider their beliefs about their illness and the degree of threat and fear experienced at the time of the event. Interventions need to help people cope with negative emotional states as well as challenging inappropriate illness beliefs.