A 29-year-old woman with systemic lupus erythematosus (SLE) presented with palpitation and neck swelling. Initial sonography showed an ill-defined hypoechoic lesion in the right thyroid gland, mentioning subacute thyroiditis. The patient received conservative care for one week. However, her neck swelling worsened and she complained of dyspnea. Follow up sonography showed marked enlargement of both thyroid glands. Irregular infiltration of hypoechoic lesions was detected along the subcapsular region of both thyroid glands. She underwent immediate intubation to secure the airway and total thyroidectomy. Histopathological staining revealed features of fungal thyroiditis with fungal hyphae characteristic of Aspergillus. There was no abnormality in the lung or paranasal sinuses. In this report, we describe the sequential sonographic findings of invasive aspergillosis in the thyroid gland presenting as progressive enlargement without other organ involvement.