The objectives of this study were to examine the prevalence of overactive bladder (OAB), including both with and without urinary incontinence, in patient with diabetes, and to explore factors related to the presence of OAB. This was a single-center, cross-sectional prospective survey. Patients with diabetes aged ≥18 years were consecutively enrolled in this study. Items related to OAB symptoms, neuropathic symptoms, clinical characteristics regarding diabetes management, and demographics were collected. The presence of OAB was assessed using the Overactive Bladder Symptoms Score (OABSS). Relationships between presence of OAB and potential related factors were explored by logistic regression analysis. The prevalence of OAB in the study cohort (n=652) was 24.2%, of which 71.5% was dry OAB (without urgency incontinence). Multivariate analysis showed that age (odds ratio [OR] 1.64, 95% confidence interval [CI] 1.07-2.50) and symptomatic diabetic polyneuropathy (DPN) (OR 2.41, 95% CI 1.64-3.54) were significantly related to the presence of OAB. The OAB prevalence in our sample of patients with diabetes was approximately 2-fold higher than that of the Japanese general population, which was based on results obtained from questionnaires similar to the present study, although the OAB prevalence of 24.2% may slightly differ from the true value due to assessment of OAB using the questionnaire only. As OAB which is deteriorated QOL can be identified and treated, screening of OAB in patients with diabetes who have DPN or aged ≥65 years may contribute to achieving the therapeutic aim of maintaining QOL.