Introduction:The association between type 1 diabetes (T1D) and other auto-immune diseases is well known. However, a quantitative overview of all associated auto-immune diseases and their prevalence in T1D is lacking. Methods: We searched PubMed, Web of Science, EMBASE and Cochrane library in September 2018 to identify relevant articles about the prevalence of the following associated auto-immune diseases in T1D cohorts: auto-immune thyroid disease, celiac disease, gastric autoimmunity including pernicious anemia, vitiligo and adrenal gland insufficiency. A meta-analysis was performed to estimate pooled prevalence using a random-effects model. Furthermore, randomeffects meta-regression analysis was performed to assess the association between prevalence and mean age or diabetes duration. Results: One hundred eighty articles were eligible including a total of 293 889 type 1 diabetes patients. Hypothyroidism (65 studies) was prevalent in 9.8% (95% CI: 7.5-12.3) of patients. Meta-regression showed that for every 10-year age increase, hypothyroidism prevalence increased 4.6% (95% CI: 2.6-6.6, P < 0.000, 54 studies). Weighted prevalence of celiac disease was 4.5% (95% CI: 4.0-5.5, 87 studies). Gastric autoimmunity was found in 4.3% of patients (95% CI: 1.6-8.2, 8 studies) and vitiligo in 2.4% (95% CI: 1.2-3.9, 14 studies) of patients. The prevalence of adrenal insufficiency was 0.2% (95% CI: 0.0-0.4, 14 studies) and hyperthyroidism was found in 1.3 percent (95% CI: 0.9-1.8, 45 studies) of type 1 diabetes patients. For all analyses, statistical heterogeneity between studies was moderate to high. Conclusions: The prevalence of antibody-mediated auto-immune disease is high among type 1 diabetes patients. Especially hypothyroidism and celiac disease are frequently found.