Context: The long-term consequences of subclinical hypercortisolism (SH) in patients with adrenal incidentalomas (AIs) are unknown. Setting and Patients: In this retrospective multicentric study, 206 AI patients with a ≥5-year follow-up (median, 72.3 mo; range, 60–186 mo) were enrolled. Intervention and Main Outcome Measures: Adrenocortical function, adenoma size, metabolic changes, and incident cardiovascular events (CVEs) were assessed. We diagnosed SH in 11.6% of patients in the presence of cortisol after a 1 mg-dexamethasone suppression test >5 μg/dL (138 nmol/L) or at least two of the following: low ACTH, increased urinary free cortisol, and 1 mg-dexamethasone suppression test >3 μg/dL (83 nmol/L). Results: At baseline, age and the prevalence of CVEs and type 2 diabetes mellitus were higher in patients with SH than in patients without SH (62.2 ± 11 y vs 58.5 ± 10 y; 20.5 vs 6%; and 33.3 vs 16.8%, respectively; P < .05). SH and type 2 diabetes mellitus were associated with prevalent CVEs (odds ratio OR, 3.1; 95% confidence interval CI, 1.1–9.0; and OR, 2.0; 95% CI, 1.2–3.3, respectively), regardless of age. At the end of the follow-up, SH was diagnosed in 15 patients who were without SH at baseline. An adenoma size >2.4 cm was associated with the risk of developing SH (sensitivity, 73.3%; specificity, 60.5%; P = .014). Weight, glycemic, lipidic, and blood pressure control worsened in 26, 25, 13, and 34% of patients, respectively. A new CVE occurred in 22 patients. SH was associated with the worsening of at least two metabolic parameters (OR, 3.32; 95% CI, 1.6–6.9) and with incident CVEs (OR, 2.7; 95% CI, 1.0–7.1), regardless of age and follow-up. Conclusion: SH is associated with the risk of incident CVEs. Besides the clinical follow-up, in patients with an AI >2.4 cm, a long-term biochemical follow-up is also required because of the risk of SH development.