Acute hepatitis B is a self-limiting infection, but severe cases resulting in liver failure and death have been reported in 1% of acute hepatitis B cases. Severe acute hepatitis B is diagnosed when one of the following criteria is present: international normalized ratio (INR) >1.5, severe jaundice (total bilirubin >3 mg/dL), or encephalopathy. Severe acute hepatitis B is considered prolonged if it lasts >4 weeks. Hyperthyroidism may lead to liver cell disruption or cholestasis injury. Severe acute hepatitis B associated hyperthyroidism is a case that is very rare. We report a 37-year-old woman with severe acute hepatitis B with protracted jaundice and thyrotoxicosis. Total bilirubin levels persisted >20 mg/dL during eight weeks of treatment despite liver enzymes falling after two weeks of treatment. The patient also had a relapse of hyperthyroidism which had been on remission phase for ten years. The patient was treated with antiviral combination of tenofovir and entecavir to prevent deterioration to liver failure. Methimazole and propranolol were given to manage the patient's hyperthyroid symptoms. The association of hepatitis B with thyrotoxicosis and persistent jaundice is debatable, as is the extrahepatic manifestation of hepatitis B which trigger the relapse of hyperthyroidism. Combination management of two antivirals should be considered in protracted severe acute hepatitis to prevent liver failure.