Objective. Amino-terminal pro-brain natriuretic peptide (NT-proBNP) is synthesized in cardiac ventricles in response to volume expansion. This study evaluated NT-proBNP levels to determine the clinical correlation with the severity of hypertensive disorders complicating pregnancy. Methods. NT-proBNP levels of 95 pregnant women (severe preeclampsia [n = 26], mild preeclampsia [n = 15], gestational hypertension [n = 9], and healthy controls [n = 45]) were determined using an electrochemiluminescence immunoassay. Results. Comparisons of the mean values of NT-proBNP levels in the different groups were significantly different, as follows: 1766.43 ± 4197.39 pg/mL (median, 339.8 pg/mL) in severe preeclampsia, 214.97 ± 226.35 pg/mL (median, 152.3 pg/mL) in mild preeclampsia, 39.75 ± 24.85 pg/mL (median, 34.09 pg/mL) in gestational hypertension, and 78.78 ± 81.56 pg/mL (median, 48.54 pg/mL) in the healthy controls. The NT-proBNP levels of the patients with mild and severe preeclampsia were significantly higher than in the patients with gestational hypertension and the healthy control patients. There was no significant difference in NT-proBNP levels between patients with mild and severe preeclampsia (p = 0.17). Conclusion. In patients with mild and severe preeclampsia, NT-proBNP levels were elevated. This may reflect ventricular stress and/or subclinical cardiac dysfunction associated with preeclampsia.