Tenofovir disoproxil fumarate (TDF) is one of the first-line treatment options in chronic hepatitis B (CHB). Despite its efficacy in suppressing viral load and a high resistance barrier, long life maintenance therapy is required. Registration studies demonstrated TDF to be a safe drug. However, post-marketing experience reported cases of serious nephrotoxicity associated with hypophosphatemia, osteomalacia and, even more recently, Fanconi syndrome associated with TDF therapy in CHB monoinfected patients.Here the authors report a case of a 40 year-old male, with a CHB monoinfection, that, three years after TDF therapy, developed a progressive chronic kidney disease with a serious hypophosphatemia and a secondary osteomalacia that was manifested by bone pain and multiple bone fractures. Further investigational analyses unveiled a proximal renal tubular dysfunction, which fulfilled most of the diagnostic criteria for a Fanconi syndrome. After TDF withdrawal and oral supplementation with phosphate and calcitriol, his renal function stabilized (despite not returning to normal), proximal renal tubular dysfunction abnormalities resolved as well as osteomalacia. In conclusion, physicians should be aware that, in CHB monoinfected patients under TDF therapy, serious renal damage is possible and preventable by timely monitoring serum creatinine and phosphate.