Today, antithyroid drugs are widely used in the treatment of hyperthyroidism. Elevated creatine kinase and liver injury (hepatitis) caused by methimazole are some of rare side effects. Elevation of creatine kinase (CK) should be monitored due to the risk of rhabdomyolysis development. Also, drug-induced liver injury can be seen. In this article, we report a patient who was put on methimazole 2 months ago for hyperthyroidism, but then began to have complaints about muscle pain, jaundice (icterus) in the eyes along with itching and dark urine, and found out to have elevated creatine kinase as well as liver enzymes induced by liver injury, thus showed rapid recovery upon N-Acetyl Cysteine (NAC) treatment.