Myxedema coma is an emergency that develops from non-diagnosed or severe hypothyroidism and requires early recognition and management. Cardiac manifestations are uncommon and pose a challenge in the recognition of myxedema coma. We present the case of a 76-year-old male with a history of thyroidectomy secondary to a follicular carcinoma, who presented with dyspnea, generalized edema, drowsiness, disorientation, memory loss, and episodic generalized tonic-clonic seizures. Antiepileptic and diuretic treatment for seizures and heart failure exacerbation did not improve the symptoms. Further blood analysis revealed a thyroid-stimulating hormone and free thyroxine of 163 mUL/L and 0.64 ng/dL, respectively. Treatment with intravenous hydrocortisone and levothyroxine led to progressive clinical improvement. Uncommon clinical manifestations such as cardiac and non-specific neurologic symptoms should be considered as manifestations of myxedema coma. A comatose mental status is not a universal manifestation, and milder symptoms should be considered. An adequate assessment, including diagnostic scores and prompt hormonal supplementation prevents fatal consequences.