Thyroid eye disease (TED), also known as Graves' orbitopathy or ophthalmopathy (GO) or Graves' eye disease, is an autoimmune condition of the retroocular tissues associated with Graves' disease. In isolated GO, the patient can present without thyroid hormone dysfunction or systemic symptoms of Graves' disease, in which case it is called euthyroid Graves' ophthalmopathy (EGO). It is very rare for this condition to have negative thyroid-stimulating hormone receptor (TSHR) autoantibodies, and we present such a rare case of a young female, who had progressive bilateral vision loss, intermittent left-sided retroocular headache, and severe bilateral proptosis. The patient was diagnosed with EGO based on multidisciplinary consults, diagnostic orbital magnetic resonance imaging (MRI) results, and a good response to treatment with intravenous steroids. Later, the patient was followed as an outpatient and treated with thyroid orbitopathyspecific immunotherapy with teprotumumab. The patient's response to teprotumumab was excellent and caused significant improvement in visual acuity, proptosis, and chemosis. This adds valuable literature to the medical field and gives insight to clinicians to consider the diagnosis of GO even with seronegative TSHR autoantibodies and euthyroid hormone status. It also adds to the understanding of the complex pathophysiology of this rare condition.