Turner syndrome (TS) is associated with an increased frequency of autoimmunity. Frequently observed autoimmune diseases in TS are also seen in the autoimmune polyendocrine syndrome type I (APS I), of which Addison disease is a key component. An overlapping antibody profile between TS and APS I could be considered. The aim of this work was to study women with TS regarding 21-hydroxylase (21-OH) antibodies and interferon omega (IFN-ω) antibodies, a highly specific marker for APS I, to determine if there are immunological overlaps between TS and APS I. Blood samples from 141 TS were assayed for 21-OH antibodies and IFN-ω antibodies using in-vitro-transcribed and translated autoantigen. Indices with a cut-off point of 57 and 200 for 21-OH antibody and IFN-ω antibody were used as reference. The median age of TS was 31·6 years (range = 11·2–62·2). Positive indices of 21-OH antibodies were present in six TS (4%), with a mean of 144·8 (range = 60–535). None had apparent adrenal insufficiency. There was no age difference comparing 21-OH antibody-positive TS (median age = 33·9 years, range = 17·7–44·7) and 21-OH antibody-negative TS (median age = 31·6 years, range = 11·2–62·2) (P = 0·8). No TS was positive for IFN-ω antibodies (mean = 42·4, range = –435–191). No overlapping autoimmune profile between TS and APS I was found. Autoimmunity against 21-OH among TS patients was more prevalent than previously identified, suggesting an increased risk of adrenal failure in TS. However, whether adrenal impairment will develop remains unknown.