OBJECTIVE The purpose of the study was to investigate the effects of a high-protein (HP) diet on bone metabolism in rats with adriamycin (ADR)-induced nephrotic syndrome. METHODS Nephrotic syndrome was established by weekly injections of ADR (2 mg/kg, i.p.) for 6 weeks. After a final injection, we confirmed that nephrotic syndrome had developed. Then, the rats were divided into two groups for the dietary treatments, namely the HP diet (30% of calories from protein) and the low-protein (LP) diet (7% of calories from protein), and were fed an isocaloric diet for the following 5 weeks. RESULTS Urinary protein and phosphate excretion were significantly greater in the HP diet group than in the LP diet group (p < 0.05). Serum parathyroid hormone and osteocalcin levels were significantly higher and lower, respectively, in the HP diet group (p < 0.05). Femur weight, femur mass index and femur calcium contents were significantly lower in the HP diet group than in the LP diet group (p < 0.05). Bone mineral density was significantly lower in the HP diet group than in the LP diet group (p < 0.05); however, bone mineral content did not differ between the two groups. CONCLUSIONS We confirmed that an HP diet negatively affects bone mineral metabolism and bone density in ADR-induced nephrotic syndrome rats.