Background: Nephrotic syndrome (NS), which accounts for 40% of renal morbidities in Egypt, is thought to be the most common kidney illness in Africa. Objective: This study aimed to evaluate the role of IgM in early diagnosis of nephrotic syndrome of steroid resistant in children. Patients and methods: This cohort study included 48 children with NS. It was conducted in the Pediatrics Nephrology Unit, Faculty of Medicine at Zagazig University Pediatric Hospitals. Patients were divided into Group (A) 24 children: new cases of nephrotic syndrome with steroid resistance. All patients were in the active stage of the disease (heavy proteinuria >40 mg/m2 /hour, hypoalbuminemia <2.5 g/dL, edema and hyperlipidemia) and Group (B): included 24 children with steroid sensitive nephrotic syndrome. Results: There was a significant higher percent of infection of steroid resistant nephrotic group compared to steroid sensitive nephrotic group. There was a significant higher percent of albuminuria and lower 24 hours protein in urine of steroid resistant nephrotic group compared to steroid sensitive nephrotic group. There was a significant lower serum total protein of steroid resistant nephrotic group compared to steroid sensitive nephrotic group. There was a significant lower serum IgG and IgM of steroid resistant nephrotic group compared to steroid sensitive nephrotic group. Conclusion: Serum IgM and IgG levels have prognostic value in patients with nephrotic syndrome and can predict the outcome and the frequency of recurrence of the disease.