We present the case of a 56-year-old man with a renal artery thrombosis. The patient’s medical history was significant for a myocardial infarction 1 year earlier. There was no history of trauma, smoking, hypertension, or diabetes mellitus. In addition to the unilateral renal arterial thrombosis, our patient had hyperhomocysteinemia, a low cobalamin level, and a heterozygous C677T mutation of the methylene tetrahydrofolate reductase (MTHFR) gene. The homocysteine level decreased with cobalamin treatment. Other causes of thrombophilia were ruled out. In the current patient, we suggest that the cause of the previous myocardial infarction and recent renal artery thromboembolism might have been associated with the effects of hyperhomocysteinemia, a low cobalamin level, and presence of a heterozygous C677T mutation of the MTHFR gene.