Objective: This study was to investigate the relationship between the progression of Diabetic nephropathy (DN) and Coronary artery calcification score (CACS) in Japanese patients with Type 2 Diabetes mellitus (T2DM) at baseline and over 5 years of follow-up. Methods: A total of 107 patients with T2DM who underwent coronary computed tomography (CT) angiography using multidetector CT and were assessed for DN each year were studied. Patients were divided into two groups based on the median CACS derived from the Agatston score. Kaplan-Meier analyses were performed to examine whether the relationship between CACS and DN progression was different between the sexes. Results: Over a 5-year follow-up, men in the high CACS group demonstrated more DN progression compared with those in the low CACS group. In male patients without diabetic retinopathy (DR), those in the high CACS group also had significantly higher DN progression than those in the low CACS group. Patients with DR in the high and low CACS groups did not have a significantly different rate of DN progression. In women, DN progression was not significantly different between the high and low CACS groups. Conclusions: In men with T2DM, CACS is a good predictor of DN progression. Overall, DN progression was not related to the presence of DR, suggesting that the progression of DN in men may be affected by atherosclerotic factors more than in women.