BACKGROUND: Mineral bone disorder (MBD) is a systemic disorder associated with chronic kidney disease (CKD). Online hemodiafiltration (OL-HDF) combines hemodialysis (HD) and hemofiltration and has shown promising results in children with CKD-5d considering co-morbidities. METHODS: Children with CKD-5d who were stable for at least 3 months on thrice weekly 3-h HD sessions via an arteriovenous fistula (AVF) using polysulphone membrane were shifted to post-dilution OL-HDF and followed up for 12 months. Baseline Ca, PO4, serum albumin, alkaline phosphatase, iPTH, CRP, soluble Klotho, FGF-23, BALP and TRAP-5b were assessed and repeated at the end of the 12-month follow-up period. RESULTS: We included 31 children (17 males) with median age of 12.5 (IQR = 9.7-13.3) years and median HD vintage of 60.1 (IQR = 9.1-37.5) months. OL-HDF resulted in a statistically significant decrease in FGF-23 and FGF-23/Klotho ratios and insignificant increase in the levels of Klotho compared to their baseline values. It also led to statistically significant increase in BALP, decrease in TRAP-5b and elevation of the BALP/TRAP-5b ratio compared to their baseline values. A 12-month period of OL-HDF treatment had no significant effect on height Z-score before and after exclusion of patients having deformities of lower limbs. CONCLUSION: OL-HDF resulted in a significant decrease in FGF-23, TRAP-5b and FGF-23/Klotho ratio with a significant increase in BALP and BALP/TRAP ratio. This might signify a promising positive impact on bone turnover in children with CKD-5d.