Background: Diabetic patients often develop urinary tract infections (UTI). Diabetic patients are also likely to develop mental illness, and psychotropic drugs have anticholinergic adverse effects such as urinary disturbance. We aimed to elucidate the risk factors of asymptomatic pyuria in patients with type 2 diabetes. Methods: We picked up outpatients with type 2 diabetes who visited the Department of Internal Medicine for the first time, from December 2010 to November 2012 for the treatment of diabetes and completed the questionnaire to obtain the medical history. We obtained clinical information from medical records and questionnaires. Urine leukocytes >= 10/high-power field was defined as pyuria. Comparisons such as pyuria group vs. non-pyuria group and non-mental illness group vs. mood disorder group vs. schizophrenia group were performed. Results: One hundred twenty-one patients were eligible. Sixty-nine were males, 52 were females, mean age was 63 years. There were 48 patients who had mental illness. The duration of diabetes was 5.1 years, hemoglobin A1c (HbA1c) was 8.5%. Prevalence of pyuria was 15.7%. Mean age in non-pyuria group was 62.8 years old, and 65.1 years old in pyuria group. Proportion of female (84%) in pyuria group was significantly higher than non-pyuria group. Patients with pyuria significantly more often had mental illness and psychotropic drugs prescription than patients without pyuria. Duration of diabetes in non-pyuria group was 5.3 years and that in pyuria group was 4.0 years. Coefficient of variations of R-R intervals (CVR-R) in electrocardiogram (ECG), an index of autonomic nervous dysfunction, was 3.2% in non-pyuria group and 1.8% in pyuria group. Pyuria group had significantly higher prevalence of autonomic nervous dysfunction. Coexistence of mental illness and lower CVR-R were associated with risk of pyuria in female diabetic patients. Conclusions: In addition to female sex, autonomic neuropathy and mental illness were significant risk factors for pyuria in patients with type 2 diabetes. To elucidate this association, further studies, preferably with larger numbers of subjects, will be needed. J Endocrinol Metab. 2019;9(6):193-198 doi: https://doi.org/10.14740/jem629