A 72-year-old male presented with a fever and altered mental status. While initially diagnosed with sepsis due to cholangitis, he continued to decline and had seizures that complicated the course. After extensive workup, he was found to have anti-thyroid peroxidase antibodies and diagnosed with steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT). He showed remarkable improvement with glucocorticoids and intravenous immunoglobulins. SREAT is a rare autoimmune encephalopathy characterized by elevated serum titers of antithyroid antibodies. SREAT needs to be listed as a differential diagnosis in a patient with encephalopathy of unclear causes, and the presence of antithyroid antibodies is a hallmark of the entity.