Little is known regarding rates of fearing hypoglycemia and predictive factors in Japan. The aim of the study was to investigate the prevalence of a fear of hypoglycemia and predictive factors in patients with Type 1 Diabetes Mellitus (T1DM). A questionnaire survey on hypoglycemia and patient-physician communication was conducted in 197 patients with insulin-treated T1DM patients at 16 hospitals and clinics. The rate of fearing hypoglycemia was 22.1%. A multivariate-adjusted logistic regression analysis found that aging (Odds Ratio [OR]: 1.02; 95% Confidence Interval [CI]: 1.00-1.04; P=0.049) and Severe Hypoglycemia (SH) during the past 1 year (OR: 4.34; 95% CI: 1.45-13.00; P=0.009) were significant determinants of a fear of hypoglycemia. Patients with such a fear showed a significantly higher frequency of talking with physicians compared to patients without such a fear, but there was no difference in carrying a diabetic data book or the possession of glucagon. Interventions to reduce fears of hypoglycemia are needed in the future.