Nephrotic syndrome (NS) represents a heterogenous group of glomerular disorders occurring mainly in children. Accumulated data suggest that patient with NS have an immunological basis. This cross-sectional comparative study was conducted in the Department of Paediatrics, Mymensingh Medical College Hospital (MMCH), Mymensingh during the period of March 2018 to October 2019 to determine the relationship of serum IgE level in frequent relapse and infrequent relapse nephrotic syndrome in children. Thirty cases of frequent relapse and 30 cases of infrequent relapse idiopathic nephrotic syndrome who were admitted in Department of Paediatrics, MMCH were included in this study by purposive sampling technique. After admission written informed consent from parents or guardians obtained. Serum IgE level was measured in all patients of idiopathic nephrotic syndrome during relapse and again four weeks after steroid therapy when patient was in remission. Serum total IgE levels were measured by ADVIA centaur CP immunoassay system. Most of the patient's age was within 2-6 years in both groups. Male children were predominant in both groups. Most of the patients came from rural area. Frequency of relapse per year was significantly higher and 24 hours urine output was significantly lower in frequent relapse nephrotic syndrome than that of infrequent relapse nephrotic syndrome. Significantly higher mean IgE was found in children with frequent relapse nephrotic syndrome (1439.8±388.5 IU/ml during relapse and 852.3±103.7 IU/ml at remission) than infrequent relapse nephrotic syndrome (1109.5±248.3 IU/ml during relapse and 776.6±108.5 IU/ml at remission) at both relapse and remission state. A linear, positive, significant correlation was found between rate of relapse and serum IgE level (Pearson correlation coefficient, r=0.674). Based on results it is concluded that serum IgE is high in relapsing nephrotic syndrome and it is persistently and significantly higher in frequent relapse nephrotic syndrome than infrequent relapse nephrotic syndrome.