Background. Thyroid abscesses are a rare condition involving neck infection. Diagnosis of this condition is often delayed when the patient presents with fever. The presence of a neck mass and verification through fine-needle aspiration may confirm the diagnosis. Methods. We report a case of a thyroid abscess with aspergillosis infection in which the diagnosis was verified through fine-needle aspiration. Results. A 67-year-old woman with underlying primary Sjogren's syndrome and autoimmune hepatitis presented with fever, chills, neck masses, and neck stiffness. Laboratory data revealed elevated C-reactive protein and normal thyroid function. Thyroid ultrasonography revealed multiple hypoechoic nodules. Thus, fine-needle aspiration was performed over the right upper nodule, and thyroid abscess with aspergillosis infection was diagnosed using cytology with cell block and fungus culture. Her symptoms improved after abscess drainage and antifungal agent treatment. Conclusion. Thyroid abscesses should be considered in patients who experience fever with a neck mass. Moreover, although aspergillosis infection in thyroid abscesses is rare, clinicians should consider the condition in differential diagnoses, particularly when the patient is immunocompromised. Thyroid ultrasonography, fine-needle aspiration, and culture are essential for diagnosis.