Background: Thyroid storm (TS) is an acute and critical presentation of hyperthyroidism. It can lead to multiple organ dysfunction and has a high rate of mortality. Heart failure is one of the grave complications of hyperthyroidism and thyroid storm. Rapid progression of TS can lead to hypoperfusion and shock even with normotensive blood pressure and normal hemodynamic parameters. Unfortunately, the prevalence of hyperthyroidism is high in developing areas that lack of advanced medical facilities. This case presentation aims to present the rare condition of acute high-output failure secondary to thyroid storm with hypoperfusion and normotensive shock. Case Illustration: A 28-year-old man came to the emergency department of a private hospital in East Borneo with worsening dyspnea on effort for three days before admission. His blood pressure was 169/103 mmHg with an irregular heart rate at 135-148 bpm. His axillary temperature was 37.9°C. ECG showed rapid Atrial Fibrillation (AF) with Ashman phenomenon. Chest x-ray revealed cardiomegaly with flattened cardiac waist and lung infiltrate. His echocardiogram has a hyperdynamic LV with LVEF 70%, normal RV function, concentric LV hypertrophy, and increased LAVi (51.19 mL/m2). From the initial echocardiogram hemodynamic assessment, eRAP was 15 mmHg, CO was 6.5 to 7.4 L/min, and SVR was 1167 to 1329 dyne/sec/cm-5. His peak E wave velocity was 92-95 cm/s. His fT4 was increased (100 ng/dL) while TSH was reduced (0.007 mU/L). H2FPEF score estimated 38.7% probability of heart failure with preserved ejection fraction (HFpEF). Burch-Wartofsky score was 60, suggesting thyroid storm. He was diagnosed with acute high-output heart failure secondary to thyroid storm due to uncontrolled Graves’ Disease, and AF with rapid ventricular response. During follow-up in the Intensive Care Unit (ICU), patients underwent hypoperfusion with normotensive blood pressure (normotensive shock). Norepinephrine was initiated. The patient kept deteriorating and then passed away in our critical care unit at day of the seventh day. Conclusion: Thyroid storm-induced acute heart failure might have a conundrum presentation due to normotensive and good cardiac output, giving a false impression of hemodynamic condition. Clinical presentation was very important to identify hypoperfusion, and aggressive treatment was needed to stabilize the patient's condition. © 2025 Indonesian Heart Association. All rights reserved.