Abstract Context More than half of patients diagnosed with unilateral primary aldosteronism (UPA) suffer from persisting hypertension after unilateral adrenalectomy. Objective The objective of this work is to develop and validate a nomogram-based preoperative score (NBPS) to predict clinical outcomes after unilateral adrenalectomy for UPA. Design and Setting The NBPS was developed in an Asian cohort by incorporating predictors independently associated with remission of hypertension after unilateral adrenalectomy for UPA and validated in a Caucasian cohort. Participants Participants comprised patients with UPA achieving complete biochemical success after unilateral adrenalectomy. Main Outcome Measure Measurements included the predictive performance of the NBPS compared with 2 previously developed outcome prediction scores: aldosteronoma resolution score (ARS) and primary aldosteronism surgical outcome (PASO) score. Results Ninety-seven of 150 (64.7%) patients achieved complete clinical success after unilateral adrenalectomy in the training cohort and 57 out of 165 (34.5%) in the validation cohort. A nomogram was established incorporating sex, duration of hypertension, aldosterone-to-renin ratio, and target organ damage. The nomogram showed good C indices and calibration curves both in Asian and Caucasian cohorts. The area under the receiver operating characteristic curve (AUC) of the NBPS for predicting hypertension remission in the training cohort was 0.853 (0.786-0.905), which was superior to the ARS (0.745 [0.667-0.812], P = .019) and PASO score (0.747 [0.670-0.815], P = .012). The AUC of the NBPS in the validation cohort was 0.830 (0.764-0.884), which was higher than the ARS (0.745 [95% CI, 0.672-0.810], P = .045), but not significantly different from the PASO score (0.825 [95% CI, 0.758-0.880], P = .911). Conclusion The NBPS is useful in predicting clinical outcome for UPA patients, especially in the Asian population.