Glaucoma incidence in patients with endogenous Cushing's syndrome (CS) has never been established. We aim to assess the risk for glaucoma among CS patients compared to controls and determine the age of disease onset. A nationwide retrospective matched-cohort study of patients with endogenous CS diagnosed between 2000 and 2023. Patients with CS were matched in a 1:5 ratio, with a control group individually matched for age, sex, socioeconomic status and body mass index. Main outcomes were the incidence of glaucoma and disease onset. A total of 609 patients [396 women (65%); mean age 48.1 ± 17 years] were included in the CS group and 3018 controls. Follow-up duration was 14.6 years (IQR 9.8-20.2) for the study group. The aetiology of hypercortisolism was divided into pituitary (259, 42.6%), adrenal (206, 33.8%) and unconfirmed aetiology (144, 23.6%) patients. At baseline, 44 (7.2%) CS patients had a diagnosis of glaucoma, compared with 151 (5%) controls. The overall risk for glaucoma was 74% higher in patients with CS compared with matched controls (hazard ratio = 1.74, p = 0.002). Patients with CS who developed glaucoma were younger (mean age of 62 ± 14.7 years) than controls (mean ± SD age, 62 ± 14.7 years), (p = 0.02). The overall risk for glaucoma in CS was high for both patients in remission and patients with persistent hypercortisolism (p = 0.048). Patients with active hypercortisolism experienced an earlier glaucoma onset (82.1 ± 88.0 months). Endogenous CS is associated with increased risk for glaucoma regardless of remission status and develops at a younger age compared with the general population.