Background: Primary Nephrotic Syndrome is a worldwide epidemic in pediatric nephrology. This study aimed to evaluate the impact of health instructions on knowledge and reported practice of mothers' having children newly diagnosed with nephrotic syndrome. Subject and method: A quasi-experimental (pre-post) research design and carried out in the urologic pediatric outpatient clinic at Pediatric Minia university hospital. Also, a purposive sample of eighty-five mothers who had children newly diagnosed with nephrotic syndrome. Two tools were used in this study to collect data: Tool I: Children and mothers' demographic characteristics, present the child's medical history, and mothers' knowledge level. tool II: mothers' reported practices. Results: the studied mothers having children newly diagnosed with nephrotic syndrome had unsatisfactory knowledge level regarding meaning, causes, manifestations, investigations, common treatment, and complications of nephrotic syndrome pre-health instructional program and improved after its implementation by three months with statistically significant differences. Also, more than one-third of the studied mothers had an average reported practice level in the pre-health instructional program increased to nearly two-thirds of them after three months from implementation of the health instructional program with statistically significant differences. Conclusion: health instructions program improved effectively knowledge level and reported practice of mothers' having children newly diagnosed with nephrotic syndrome. Recommendation: Perform continuous health instructions program about the nephrotic syndrome is effective especially for the newly diagnosed cases.