Background. Puerperal sepsis is infection of the genital tract occurring at any time between the onset of rupture of membranes or labor and the 42 day postpartum. It's one of the fifth common causes of maternal mortality worldwide. The aim of this study is To assess Knowledge and practices of postnatal mothers regarding prevention of puerperal sepsis . Research Design: A descriptive cross sectional research design. Subject: Purposive samples composed of (87) postnatal mothers from Minia University Hospital for obstetric and pediatric at postnatal department. Tools of data collection: include - A structured interview questionnaire, knowledge assessment tool and practical assessment tool. Results: the study revealed that (87.4%) of the studied women had unsatisfactory knowledge level regarding puerperal sepsis and (74.7%) of the studied sample had poor practice about prevention of puerperal sepsis. There is positive association between total knowledge score and total practices level (p. value < .ooo1) Conclusion: The study concluded that majority of postnatal mothers had poor level of  knowledge regarding puerperal sepsis , and around three quarters of them had poor practice about prevention of puerperal sepsis. A positive fair association was found between knowledge and practice scores regarding prevention of puerperal sepsis. Recommendation: - The obstetric nurse could play and implement their role as health educator, counselor, coordinator, and supervisor and help post natal mothers to improve their knowledge and practices regarding puerperal sepsis and its prevention.