Introduction: In recent years, chronic and persistent bacterial infections are introduced as predisposing factors of acute myocardial infarction (MI) that is a main cause of health problems, worldwide. In this study, the relationship between previous mycoplasma pneumonia infection and further myocardial infarction was investigated through seropositivity rate of mycoplasma pneumonia in patients with (MI) and control group.Materials & Methods: In this retrospective descriptive study, 374 sera of patients and 185 sera of control group were examined by a commercial quantitative specific mycoplasma pneumonia IgG-ELISA kit (EUROIMMUNE, Germany) simultaneously. The results were analyzed by Qui square test in SPSS, Ver.16 software.Findings: We found no significant relationships between seropositivity to mycoplasma pneumonia (IgG) and sex (P=0.080), age (P=0.700), occupation (P=0.080), and living place (P=0.150), but the relationship between history of previous acute febrile diseases, infective chest diseases, hypertension and MI with mycoplasma pneumonia was significant (P=0.003, P=0.004, P=0.003, P=0.003 consequently).Discussion & Conclusion: Regarding the results of this study, it can be said that history of previous mycoplasma pneumonia infections can be considered one of the etiological agents in MI.