Back ground: Evidence based guidelines after bone marrow transplantation provides nurses with the scientific research to make well-founded decisions and reduce expected complications. Aim of the study: Was to evaluate the effect of evidence based guidelines on nurses' performance to reduce complications for patients after bone marrow transplantation. Research design: Quasi experimental design was utilized. Sample: Convenient sample of all nurses (60) from both sexes who had working in bone marrow transplantation units in Tanta Educational Hospital, and Dar El Salam Cancer Center in Masr Al-Qadimah (Harmel Specialized Hospital previously) and a purposive sample of 30 adult patients from both sexes post-transplant phase were included in the study during nine months. Tools: Three tools were used, I: Structured questionnaire for nurses, II: Nurse's performance observational checklist for BMT patient and III: Patient's assessment sheet. Results: There was positive correlation between knowledge and practice at pre, post and follow up implementation of the guidelines and there was a positive correlation between total nurses' knowledge, practice and patients' early and late complications at post implementation of evidence based guidelines. Conclusion: Implementation of evidence based guidelines has appositive effect in improving nurses' knowledge and practice regarding care of patients undergoing bone marrow transplantation and reducing patients' complications. Recommendations: Evidence based guidelines regarding bone marrow transplantation should be revised periodically and be available in all hospitals in both Arabic and English language.