Objective: Type 2 diabetes mellitus (T2DM) is associated with a high prevalence of depression, and depression is influenced by personality traits; however, these psychological factors have not been well studied in individuals with T2DM. The association between the use of a 5-factor model of personality and depressive symptoms was examined in individuals with T2DM. Methods: The subjects were 435 T2DM patients (mean age 63.1±12.6 years). Depressive status and personality traits were assessed using the Center for Epidemiologic Studies Depression Scale and the Ten-Item Personality Inventory, Japanese version, respectively. Lifestyle factors and glycated hemoglobin A1c levels in the patients were also included in the analyses. Results: Among the 435 subjects with T2DM, 130 (29.9%) exhibited possible depression, and 68 (15.6%) exhibited probable depression. After adjustment for confounders, Extraversion, Agreeableness and Neuroticism were found to be significantly associated with the presence of depression. No relationships were found between depression and HbA1c. Conclusion: These findings indicate that Extraversion and Agreeableness are protective factors, and Neuroticism is a risk factor for depression in T2DM patients. Psychological therapy focusing on personality may reduce depressive symptoms. Additional studies are needed to examine the relationships between psychological factors and depressive symptoms using a longitudinal study design.