Introduction: Data shows that no study at a national level on fatality rates of myocardial infarction (MI) and its determinants in diabetic and non-diabetic hospitalized Iranian patients, has yet been published. The aim of this study was to determine the case fatality rate (CFR) of MI in patients with and without history of diabetes and the factors associated with MI mortality in Iran. Materials and Methods: In this cross-sectional, national study, data of 20,750 new patients with MI were used. For data analysis, Chi-square test, t-test and logistic regression model in Stata software were used. Modeling was done per gender. Results: Of 20,750 new patients with MI, 4,612 (22.3%) patients had diabetes. Case Fatality rates of MI were 13.22% (confidence interval [CI] 95%=12.27-14.23) in diabetic patients and 11.7% (11.28-12.26) in non-diabetic patients, and were significant (p=0.036). Odds ratio (OR) of mortality from ST segment elevation myocardial infarction STEMI was 4.77 (CI 95%=4.20-5.43) in men, approximately twice that in women (OR=2.13, CI 95%=1.78-2.54). Conclusion: Although CFR was higher in diabetic patients than in non diabetic ones, the statistically significant difference was not clinically noteworthy, due to the small difference in CFR between the two groups and large sample size of the study. Therefore, prompt management and provision of required healthcare in emergency and CCUs within the appropriate time and access to specialized treatments for diabetic and non diabetic patients are recommended.