Introduction: Nephrotic syndrome (NS) is the commonest chronic glomerular disease in children. Idiopathic NS can perfectly be controlled using corticosteroids in most instances, but a significant relapse rate of NS is still a major problem. Several treatment protocols are suggested to decrease relapse rate of NS in children. Objectives: The current clinical trial aimed at comparing the relapse rate between two 8- and 12-week steroid treatment regimens. Patients and Methods: In the current non-randomized, clinical trial, a total of 68 children with primary NS were enrolled. Oral prednisolone was administered to 34 patients for eight weeks (2 mg/kg/d and 1.5 mg/kg/alternate-day/each for four weeks) and other 34 patients for 12 weeks (2 mg/kg/d and 1.5 mg/kg/alternate-day/each for six weeks). A one-year followup was completed for all the patients to evaluate relapse rate, steroid resistance, and steroid dependence. Results: The remission rates were 47.1% and 73.5%, respectively in children of the eight- and 12-week treatment groups because the difference was significant (P=0.026). The frequent relapse rates in the eight- and 12-week treatment groups were respectively 26.5% and 11.8%. Steroid dependence rate was 17.6% and 8.8% in the eight- and 12-week treatment groups respectively. The steroid resistance rates were respectively 8.8% and 5.9% in the eight- and 12-week treatment groups. Conclusion: Twelve-week steroid treatment can significantly decrease the relapse rate in comparison with eight-week treatment because no significant difference in steroid resistance, steroid dependence, and frequent relapse between the two treatment protocols was observed.