Introduction: Kidney transplantation restores many of the disorders accompanying endstage renal disease (ESRD). However, hypophosphatemia is common complication after renal transplantation. High levels of fibroblast growth factor 23 (FGF23) and parathyroid hormone (PTH) are two suspected factors determining the hypophosphatemia after kidney transplantation. Objectives: This observational prospective study was carried out to clarify the role of mentioned factors in hypophosphatemia after kidney transplantation. Patients and Methods: Living donor kidney transplant recipients which admitted to the ward of the renal transplantation, enrolled to the study. Parameters of bone and mineral metabolism including FGF23 and intact PTH levels were assessed. Results: High FGF23 level before transplantation was related to lower phosphate levels at 3rd month after transplantation. PTH levels showed no relationship with hypophosphatemia after kidney transplantation. Conclusion: High levels of FGF23 in ESRD patients undergoing kidney transplantation is an important determinant of hypophosphatemia in long-term follow up.