Aim Obstructive Sleep Apnoea (OSA) is frequent in patients with type 2 diabetes. The aim of this study is to evaluate prevalence of OSA in patients with type 1 diabetes. Methods In a cross-sectional design, all patients with type 1 diabetes attending the outpatient clinic were offered screening for OSA for one night with the ApneaLink + home-monitoring device. OSA was classified by the Apnoea–Hypopnea index (AHI; apnoeas/hypopneas per hour sleep). Symptoms of OSA were scored using the Epworth Sleepiness Score. Presence of autonomic neuropathy was evaluated by the Vagus® device. Results A total of 200 of 518 eligible patients with type 1 diabetes (39%) participated (68% men; age 52 ± 15 years (mean ± SD), diabetes duration 24 ± 14 years and BMI 25.3 ± 3.3 kg/m2). OSA was diagnosed in 92 patients (46% (95% CI: 40–53)). Five patients had known OSA, and OSA was newly diagnosed in 87 patients, predominantly mild OSA (60 patients (69%)). OSA was present in 32% of the patients with normal BMI, in 60% of overweight patients, and in 61% of obese patients. Patients with type 1 diabetes and OSA were largely asymptomatic and did not report more sleepiness than patients without OSA. At multivariate analysis, age, BMI and presence of nephropathy were positively associated with risk of OSA. Conclusions The prevalence of asymptomatic OSA is high in a cohort of patients with type 1 diabetes. Older age, overweight, and presence of nephropathy are associated with OSA.