Melatonin is a circadian hormone with antioxidant properties that protects against myocardial ischemia-reperfusion injury. Genetic variations of the melatonin receptor 1B gene ( ) play an important role in the development of type 2 diabetes, a risk factor for cardiovascular diseases. Accordingly, polymorphisms are crucial in numerous disorders of the cardiovascular system. Therefore, the aim of the present study was to investigate a possible association of polymorphisms with chronotype and susceptibility to myocardial infarction. The present case-control study included 199 patients with myocardial infarction (MI) (57% men) and 198 control participants (52% men) without previous cardiovascular diseases who underwent genotyping for the polymorphisms rs10830963, rs1387153, and rs4753426 from peripheral blood samples. Chronotype was determined using the Morningness-Eveningness Questionnaire (MEQ). As estimated by the chi-square test, no significant association was found in the distribution of alleles and genotypes between myocardial infarction patients and controls. In addition, there was no association between polymorphisms and chronotype in MI patients. As some previous studies have shown, the present negative results do not exclude the role of the polymorphisms studied in the development of myocardial infarction. Rather, they may indicate that polymorphisms are a minor risk factor for myocardial infarction.