Objective We aimed to clarify the prevalence of preexisting Metabolic Syndrome (MetS) defined by the Japanese original criteria among patients with non-fatal myocardial infarction (MI). Methods This is a retrospective cohort study using the computer database obtained by the preliminary health checkup from April 2003 to December 2008. We extracted the subjects with newly developed nonfatal MI from the study population. The newly non-fatal MI was diagnosed by the history of coronary heart disease (CHD) and new appearance of abnormal Q wave on electrocardiograms. MetS was diagnosed by using the Japanese original criteria. If waist circumference was not available, BMI was used alternatively. We evaluated the prevalence of preexisting MetS and other risk factors of CHD among the subjects. We compared the prevalence of preexisting risk factors between MetS group and non-MetS group. Results From a study population of 298,455 subjects, 446 subjects with a history of CHD were found. Among the 446, 92 subjects (85 men and 7 women) with abnormal Q wave on electrocardiogram were found. The prevalence of preexisting MetS with non-fatal MI was 19.6% (95% CI; 15.5-23.7%). The prevalence of other preexisting risk factors were 60.0% with smoking history, 55.6% with over-work, 53.3% with stressful life and 36.1% with impaired glucose tolerance. These prevalence rates were not significantly different between MetS group and non-MetS group. Only the prevalence (22.3%) of elevated LDL-cholesterol in the non-MetS group was significantly higher than in the MetS group (14.4%). Conclusion Preexisting MetS may be able to predict only 20% of future MI. To prevent future myocardial infarction, precaution guidance may be required for people with not only preexisting MetS but also other preexisting risk factors of CHD.