Background: Although obstructive sleep apnea (OSA) frequently coexists with type 2 diabetes mellitus (T2DM), many cases remain undiagnosed, particularly among overweight or obese individuals. Objectives: This study aimed to determine the risk factors associated with OSA among overweight or obesity T2DM. Methods: A multicenter cross-sectional descriptive design was conducted from September 2023 to April 2024. A total of 422 T2DM participants were recruited from four Diabetes Shared Care Network clinics in Taiwan. The Pittsburgh Sleep Quality Index, Epworth Sleep Scale, and a portable sleep monitoring device were used for data collection. A hierarchical multiple regression analysis was conducted to identify the factors affecting T2DM patients with OSA, and a multinomial logistic regression analysis was used to examine the major influence factors for each OSA severity level. Results: 80.3% of the T2DM participants were found to have OSA; 51.8% had moderate to severe OSA. After controlling the confounding variables, age, number of comorbidities, BMI, neck circumference, snoring times, and pulse rate were significant predictors of Apnea-Hypopnea Index (AHI). Furthermore, severe OSA was significantly related to age, BMI, gender, pulse rate, and snoring times. Conclusions: Up to 80.3% of participants with T2DM were found to have OSA. Higher BMI, neck circumference, number of comorbidities, age, pulse rate, and snoring frequency were significantly associated with OSA. Notably, BMI and age were the most significant predictors across mild, moderate, and severe OSA. Therefore, it is strongly recommended that patients with overweight or obese T2DM undergo routine OSA screening to ensure timely diagnosis and optimize management.