Background: Diabetes mellitus is associated with a higher incidence of acute myocardial infarction. Objective: To study the prevalence and outcome of patients with diabetes among patients with acute myocardial infarction. Methods: Retrospectively, patients who presented with acute myocardial infarction in a 10-year period were identified from the coronary care unit database. Results: A total of 1598 Qatari patients were admitted with acute myocardial infarction, 863 (54%) of them had diabetes mellitus (females 68.5% vs males 48.3%; P <.001). In-hospital mortality rate was non-significantly higher in diabetic patients (18% vs 15% P=.15). Aspirin (odds ratio 2.39, 95% confidence interval 1.96-2.90, P =.003] and beta-blocker use (odds ratio 1.75, 95% CI 1,21-2.52, P=.0001) were independently associated with reduced mortality risk. Conclusions: The prevalence of diabetes mellitus among patients with acute myocardial infarction in a geographically defined population in the developing world is high with a trend for poor outcomes. However, mortality was not significantly higher in diabetes mellitus than non-diabetes mellitus patients.