This observational longitudinal study aimed to explore the risk factors for disabilities in older Japanese individuals with diabetes at a frailty clinic, an outpatient clinic specializing in comprehensive geriatric assessments for older patients. The outcome was the onset of disability as a new certification of long-term care needs in outpatients aged ≥65 years. Multivariable Cox regression analyses examined the independent associations between the onset of disability and the variables that reached significance in the bivariate analysis, after adjusting for age and sex, years of education, and certification of need for support. A total of 182 participants (mean age 77.8 years, 59.9% female) were included in the study. During a mean follow-up period of 1070 days, 28 patients (15.4%) developed disabilities. Multivariable analysis showed that poor glycemic control (higher levels of glycosylated albumin and HbA1c), frailty as measured by the Clinical Frailty Scale (CFS), cognitive decline as assessed by the revised Hasegawa Dementia Scale (especially "5 object recall" and verbal fluency as assessed by the number of "vegetable names"), poor adherence to medications, and reduced muscle mass were significantly associated with the development of disability. Multivariable Cox regression analyses revealed independent and significant associations between the development of disability and HbA1c ≥7.5%, CFS ≥4, and generating vegetable names≤9. In identifying older patients with diabetes who are at risk of developing disabilities, it may be useful to evaluate glycemic control, CFS, cognition, and medication adherence. Verbal fluency tests using vegetable names may serve as simple tools for assessing the risk of disability. Geriatr Gerontol Int 2024; ••: ••-••.