Adefovir dipivoxil, an acyclic nucleoside analogue, has been approved for the treatment of patients with chronic hepatitis B. This agent is efficacious particularly in those who have developed lamivudine resistance. The report according to hypophosphatemia induced by low dose adefovir therapy is very rare. We report one case in which osteomalacia with hypophosphatemia developed in a patient with chronic hepatitis B on adefovir dipivoxil at a low dose, 10 mg daily. A 66-year-old man, who had been taking adefovir for more than 4 years due to lamivudine resistance, presented with muscle weakness and bone pain in both thighs. After 3 years of adefovir therapy, hypophosphatemia and elevated serum alkaline phosphatase levels had been noted. A bone scan showed multiple hot uptakes. All the image findings and clinical symptoms, such as bone pain and muscle weakness were improved after correcting the hypophosphatemia with oral phosphorous supplementation.