Addison's disease is an autoimmune process. However, Addison's disease associated with connective tissue diseases (CTD) is only occasionally reported. Here, we report six cases of Addison's disease secondary to a variety of CTD, which include systemic lupus erythematosus, Takayasu arteritis, systemic sclerosis, ankylosing spondylitis (AS) and antiphospholipid antibody syndrome. The association of Addison's disease with Takayasu arteritis and AS is reported for the first time. We also found high prevalence of hypothyroidism as concomitant autoimmune disorder. Our case series highlight the autoimmune features of Addison's disease. Therefore, we suggest considering adrenal dysfunction in patients with CTD.