A 39-year-old woman with a 3-year history of a rounded face developed widespread myalgia. Detailed examinations revealed no disorders that could explain the pain other than concomitant Cushing's disease and central hypothyroidism. Both the hypercortisolemia and hypothyroidism completely resolved after the patient underwent surgery to treat Cushing's disease, but she continued to experience unresolved myalgia and met the diagnostic criteria for fibromyalgia. Few studies have so far investigated patients with fibromyalgia associated with Cushing's syndrome. In our case, the hypothyroidism caused by Cushing's disease probably played an important role in triggering and exacerbating fibromyalgia. This highlights the need to examine the endocrine function in patients with muscle pain.