Our purpose was to assess the relationship between serum fibroblast growth factor 23 (FGF23) and left ventricular function, carotid intima-media thickness (CIMT) and laboratory features in children on peritoneal dialysis (PD). The study population consisted of 17 patients (11 female; median age 7.83 years, range 0.66-17.75) undergoing PD for 22 months (range 2-98). Serum FGF23, serum phosphorus, calcium, intact parathyroid hormone (iPTH), 25(OH) vitamin D, 1,25(OH)2 vitamin D and Kt/V urea, left ventricular mass (LVM) and LVM index (LVMI) were assessed. Median FGF23 level was 29.92 pg/ml (22.7-74.76), phosphorus was 5.2 mg/dl (3.1-9.9), iPTH was 438 pg/ml (16-1446), 25(OH) vitamin D was 11 ng/ml (5-35), 1,25(OH)2 vitamin D was 11 pg/ml (2-106), Kt/V urea was 2.33 (1.01-3.84). FGF23 level was independently associated with Kt/V urea (p<0.001). We found that effective dialysis may be the leading determinant of FGF level, independent from the calcium-phosphorus-PTH axis, in pediatric PD patients.