Accumulated evidence has shown that low renin hypertension is common in patients with diabetic nephropathy. However, the performance of aldosterone to renin ratio (ARR) in primary aldosteronism (PA) patients with diabetes has not been well validated. Here, we report the performance of screening ARR in PA patients with diabetes. The study enrolled consecutive patients and they underwent ARR testing at screening. Then the diagnosis of PA was confirmed from the Taiwan Primary Aldosteronism Investigation registration dataset. Generalized additive model smoothing plot was used to validate the performance of screening ARR in PA patients with or without diabetes. During this study period, 844 PA patients were confirmed and 136 (16.0%) among them had diabetes. Other 816 patients were diagnosed with essential hypertension and used as the control group and 89 (10.9%) among them had diabetes. PA patients with diabetes were older and had a longer duration of hypertensive latency, higher systolic blood pressure and lower glomerular filtration rate than those PA patients without diabetes. The cut-off value of ARR in the generalized additive model predicting PA was 65 ng/dL per ng/mL/h in diabetic patients, while 45 ng/dL per ng/mL/h in non-diabetic patients. There was a considerable prevalence of diabetes among PA patients, which might be capable of interfering with the conventional screening test. The best cut-off value of ARR, more than 65 ng/dL per ng/mL/h in PA patients with diabetes, was higher than those without diabetes.