Nursing management of patient undergoing blood transfusion is important. A comprehensive understanding of blood transfusion process and areas requiring special attention would be important to reduce the complications arising from blood transfusion. All staff must be aware of all aspect of care and the principles of safe effective patient identification, using aseptic technique during transfusion, proper documentation and adequate management of adverse reactions. The aim of this study was to assess the nurses' performance (knowledge& practice) regarding management of patient undergoing blood transfusion and factors affecting nurses' performance during blood transfusion. Setting: the study was carried out at surgical and hematology departments at Ain Shams University Hospitals. Study subjects: A convenient sample of all available nurses (n=60) were included in this study, their mean age 31.6± 5.7 .Data collection tools: a) self administered questionnaire sheet. b) nurses' practice observational checklist. Results & conclusion: 70% of nurses had unsatisfactory knowledge regarding to management of patient undergoing blood transfusion and 80% of them showed unsatisfactory level of practice regarding to management of patients undergoing blood transfusion. Furthermore, there were many factors affecting nurses' performance as: nurses' related factors, work' related factors and patient' related factors. Recommendations: This study recommends the importance of in-service training courses to enhance the nurse's knowledge and practice and to avoid complications of blood transfusion.