Primary aldosteronism (PA) is considered a major cause of resistant hypertension (RHT). The prevalence of RHT has been recently reported to reach 18% in general hypertension. However, little is known about the prevalence and the outcomes after adrenalectomy of RHT in PA. Therefore, we aimed to clarify the prevalence and surgical outcomes in patients with both PA and RHT.Among 550 patients who underwent adrenalectomy for unilateral PA in the Japan Primary Aldosteronism Study, RHT was defined as an uncontrolled blood pressure (≥140/90 mmHg) despite treatment with at least any three antihypertensives or hypertension controlled with at least four drugs. Surgical outcome was assessed by the biochemical and clinical outcome.Although 40 (7.3%) patients fulfilled the criteria for preoperative RHT, this should be underestimated because only 36% of patients with postoperative RHT were classified as having preoperative RHT. The prevalence of preoperative RHT was approximately 20% when estimated using the total number of patients with postoperative RHT, and the ratio of postoperative RHT in patients with preoperative RHT. Although an improvement in hypertension was achieved in approximately 80% of patients with preoperative RHT, 20% of these exhibited persistent RHT. These patients were more obese than those for whom RHT improved after surgery. Notably, body mass index of ≥25 kg/m2 was an independent predictor of postoperative RHT.The prevalence of RHT in PA was lower than expected even with the adjustment for underestimation. Furthermore, obesity is an independent factor predicting the postoperative persistence of RHT.