Objective: The prevalence of atrial fibrillation (AF) in type 2 diabetes mellitus (DM) patients under primary care in Hong Kong was yet to be explored. We aimed to evaluate the prevalence of AF in patients with DM so as to provide evidence-based recommendations to incorporate AF screening as a component in regular diabetic risk and complication assessment. The performance of automated BP machine Microlife WatchBP Office AFIB as a screening tool for the detection of AF was also evaluated.Method This was a cross-sectional study. Patients with type 2 DM who attended the regular diabetic risk and complication assessment in the participating clinics from 24 August 2021 to 27 January 2022 were recruited. Blood pressure measurement by Microlife WatchBP Office AFIB and 12-lead ECGs were performed for AF screening. Results: Among 2015 DM patients in primary care, the prevalence of AF was found to be 1.9% (95% confidence interval [CI] 1.3–2.6). The prevalence of AF increased with age, from 0.5% in patients aged < 65 years, to 2.2% in patients aged 65–74 years and 4.3% in patients aged ≥ 75 years. The sensitivity and specificity of Microlife WatchBP Office AFIB to detect AF were 80% (95% Cl 61.8–92.3) and 97.9%. (95% CI 97.3–98.5), respectively. The positive and negative predictive values were 32.8% (95% CI 21.9–45.1) and 99.7% (95% CI 99.5–99.9) respectively. Conclusions AF screening with the use of Microlife WatchBP Office AFIB is a simple procedure and can be considered as a standard assessment in the regular comprehensive diabetic risk and complication assessment in primary care setting.