Primary aldosteronism (PA) is the most frequent form of secondary hypertension, but diagnostic tools for this disease still lack optimal accuracy. The heart is one important target tissue for damage due to excess aldosterone, and the role of natriuretic peptides is well recognized in diagnosing heart failure. We hypothesized that measuring the NT-proBNP could improve the diagnostic evaluation of PA. We enrolled 132 hypertensive patients, who underwent aldosterone to renin ratio (ARR) screening, and 81 underwent an intravenous saline loading test (ivSLT) because of a high ARR. The NT-proBNP level positively correlated with the ARR and inversely correlated with the renin level. The NT-proBNP level was higher in patients with a high ARR than in those with a low ARR and higher in patients with a positive ivSLT than in those with a negative ivSLT. After logistic regression analysis, an NT-proBNP value above the median and male gender were predictors of a positive ivSLT. The proportion of patients with a positive ivSLT ranged from only 23 % in females with a low NT-proBNP to 93 % in males with a high NT-proBNP. NT-proBNP and gender are predictors of a positive PA confirmatory test. These findings highlight the possibility of using NT-proBNP to identify which patients with a high ARR should receive a complete PA diagnostic evaluation.