Background: Postpartum hemorrhage (PPH) prevention  is  the  main  stay  and  corner  stone  to  achieve  the millennium developmental goal 5 (MDG5). Maternity nurses play a crucial role in maternal morbidity reduction resulting from PPH and competency of maternity nurses directly affects quality of treatment and health outcomes. Aim: was to develop competences for maternity nurses during labor regarding prevention of primary postpartum hemorrhage. Design: A quasi-experimental design was used. Setting: The research was carried out in maternity hospital at Zagazig university hospitals, Sharkia Governorate, Egypt. Subjects: purposive sample included fifty nurses provided direct nursing care for women during labor and postpartum period. Tools: Three tools were used; a structured interviewing questionnaire,competency performance checklist for maternity nurses' practice regarding prevention of primary postpartum hemorrhage, maternity nurses attitude scale regarding prevention of primary postpartum hemorrhage. Results: The results of this study showed that there was an improvement in nurse's knowledge, practice and attitudes toward prevention of primary postpartum hemorrhage after implementation of competency nursing intervention. Also, there were positive correlation between nurses' knowledge score and their attitude scores, practice scores and age. Conclusion: there was highly statistically significant improvement in nurses' knowledge and practice level during labor to prevent primary PPH after implementation of competency nursing intervention compared to pre intervention. Recommendations: Offer training programs or workshops for developing the nurses' competency regarding primary postpartum hemorrhage prevention to develop their best practice.