Recurring nature of idiopathic nephrotic syndrome (INS) and steroid dependence imply a long-term treatment with glucocorticosteroids (GCSs), which increases the risk of bone metabolism disorders. The search for new markers of that process is essential. The aims of this study were to assess the concentrations of sclerostin (Scl) and fibroblast growth factor-23 (FGF-23) in the plasma of children with INS and compare Scl and FGF-23 to existing markers of bone metabolism, mainly parathyroid hormone (PTH). The study involved 70 children, 50 with INS and 20 healthy children. Patients with INS were divided into 4 groups depending on the number of relapses and applied therapy. Significantly higher concentrations of FGF-23 and Scl were found in all patient groups with INS compared to the control group, and increase in the concentrations of examined parameters depending on the number of NS relapses was showed. In patients from the group with numerous relapses, higher concentrations of FGF-23 and Scl in the relapse phase than those in the remission phase were found. We observed positive correlation in these proteins with parathyroid hormone. Positive correlation of FGF-23 and Scl in the examined group was noted. Children having relapsing INS treated with steroids have higher levels of Scl and FGF-23 that can indicate the bone metabolism disorders. The significance of these observations requires further research.