Background: Postpartum hemorrhage (PPH) continues to be the leading cause of maternal morbidity and mortality in most countries around the world. Aim: The goal of the study was to evaluate application of WHO guidelines regarding prevention and management of postpartum hemorrhage on nurses’ competence. Subjects and method: Research design: the current study used a quasi-experimental design. Setting: The study was carried out in in Obstetrics & Gynecology Specialized hospital affiliated of Comprehensive Health Insurance to Port Said city. Sample: A convenience sample of all nurses (150 nurses) in Obstetrics & Gynecology Specialized hospital who working at time of study were included in the study. Data collection tools: the initial tool, structured interviewing form, the second tool, Nurses’ competency toward prevention of postpartum-hemorrhage, the third tool, Nurses' practice observational checklist and the last tool, Self-confidence measurement Scale. Results: The present study showed that all of the studied nurses had poor overall knowledge and negative attitude regarding prevention and management of postpartum hemorrhage pre applying WHO guidelines. Also, the vast majority of the studied nurses reported unsatisfactory practice regarding prevention and management of post partum hemorrhage. But, there were a marked improvement of the studied nurses' knowledge, attitude and practice post applying WHO guidelines for prevention and management of post-partum hemorrhage. Conclusion: The current study found that application of WHO guidelines was effective in achieving the aim of enhancing nurses’ competence and their self-confidence regarding prevention and management of post partum hemorrhage among the studied nurses. Recommendations: Implementing of periodical health education programs for intern nurses to enhance competent skills for achieving advanced nursing care regarding prevention and management of primary postpartum hemorrhage.