Because living alone is associated with an increased risk of type 2 diabetes mellitus in men but not women, living alone may be a risk factor of cardiovascular events after acute myocardial infarction (AMI) in diabetic men. The aim of the present study was to investigate the association between living alone and mid-term clinical outcomes after AMI in diabetic men. We conducted a single center, retrospecitve study. The primary endpoint was the major adverse cardiovascular events (MACE) defined as the composite of all cause death, AMI, and target vessel revascularization. A total of 253 AMI men with diabetes mellitus were included from our hospital records, and divided into the living together group (n = 203) and the living alone group (n = 50). Median follow-up duration was 239 days (Q1: 94 days, Q3: 451 days). A total of 66 MACE was observed during the study period, and Kaplan–Meier curves were constructed to compare the MACE. The MACE was more frequently observed in the living alone group than the living together group (P = 0.041). Multivariate Cox regression analysis revealed that the living alone group was significantly associated with the MACE (Odds ratio: 1.770, 95% confidence interval 1.018–3.077, P = 0.043) after known clinical risk factors. In conclusion, living alone was significantly associated with the mid-term MACE after AMI in diabetic men. It may be important to provide multiple interventions including lifestyle guidance as well as sufficient acute medical care for such high-risk patients.