In rats with aldosteronism, a reduction of bone mineral density (BMD) and cortical bone strength has been reported. Our study was aimed to evaluate bone involvement in patients with primary aldosteronism (PA). A total of 188 consecutive subjects with adrenal incidentaloma, observed between November 2009 and October 2011, were screened for PA with aldosterone‐to‐renin ratio. After confirmatory tests, in those who screened positive, 11 patients were diagnosed as PA and 15 patients were not (nPA). A serum/urinary biochemical profile, parathyroid hormone (PTH), BMD measured at lumbar spine (LS) and total and femoral neck (TN and FN) by dual X‐ray absorptiometry, and conventional spinal radiographs (T4–L4) were obtained in all subjects. PA patients had a significantly higher 24‐hour urinary calcium (6.28 ± 1.85 versus 4.28 ± 1.18 mmol/d; p < 0.01), and PTH (9.8 5.8‐14.6, median range versus 5.3 2.5‐10.8 pmol/L; p < 0.01) than nPA patients. BMD expressed as Z‐value at LS (−1.18 ± 0.99 versus 0.22 ± 1.12), FN (−0.85 ± 0.73 versus 0.01 ± 0.82), and TN (−0.49 ± 0.61 versus 0.39 ± 0.93) was lower in PA than in nPA (p = 0.003, p = 0.011, and p = 0.012, respectively). The prevalence of osteoporosis was higher in PA than in nPA (8/11, 72.7% versus 3/15, 20.0%; Fisher's exact test: p = 0.015). Vertebral fractures tended to be more prevalent in PA than in nPA (5/11, 45.5% versus 2/15, 13.3%; Fisher's exact test: p = 0.095). Logistic regression analysis showed that osteoporosis and morphometric vertebral fractures were associated with PA (odds ratio OR, 15.4; 95% confidence interval CI = 1.83–130, p = 0.012; and OR, 30.4; 95%CI, 1.07–862, p = 0.045, respectively) regardless of age, body mass index (BMI), and LS‐BMD. In 9 of 11 PA patients, 6 months after beginning of treatment (surgery or spironolactone) there was a significant reduction of urinary calcium excretion (p < 0.01) and PTH (p < 0.01), whereas in 5 of 11 PA patients, 1 year after beginning of treatment, BMD was significantly increased at LS, p < 0.01). In conclusion, PA is associated with osteoporosis, vertebral fractures, and increased urinary calcium excretion. © 2012 American Society for Bone and Mineral Research.