Introduction: Entecavir, a nucleoside analog (NA), is effective for treatment of chronic hepatitis B virus (HBV) infection. Methods: We report the case of a patient we encountered with entecavir-associated myopathy. We also performed a literature review of myopathies associated with nucleoside analogs. Results: A 44-year-old man presented with a 3-month history of myalgia and progressive weakness. He had HBV infection and had received entecavir antiviral treatment for 5 years. Laboratory tests showed that serum creatine kinase levels were significantly elevated. Muscle histopathology showed abundant T-lymphocyte infiltration of muscle fibers, and HBV surface antigen and HBV core antigen were not present in muscle fibers. Entecavir-associated myopathy was subsequently diagnosed. The patient's symptoms eventually resolved, and serum CK levels decreased rapidly after he stopped receiving entecavir treatments. Conclusions: Patients who receive NA therapy should be closely monitored for myopathic side effects. Muscle Nerve 49:610-614, 2014