Abstract Background: The aim of the study was : To assess nurses' knowledge and practice regarding patients undergoing coronary artery bypass graft surgery, to design nursing care protocol for nurses, and to evaluate the effect of implementing the designed nursing protocol on nurse's knowledge and practice. Three hypotheses were formulated: (1) the post mean knowledge scores of nurses who will expose to designed nursing protocol will be higher than their pre mean knowledge scores. (2) The post mean practice score of nurses who will expose to designed nursing protocol will be higher than their pre mean practice scores. (3) A positive relationship will exist between knowledge and practice score obtained by nurses receiving the designed nursing protocol. Research design: Quasiexperimental research design was utilized in this study. Tools: Three tools were utilized for data collection were a) structured interview sheet. b) Observation checklist sheet. c) Construction of designed nursing protocol. Results The first and the second hypotheses were supported as a good improvement in the mean knowledge & practice scores. Conclusion: implementing of designed nursing protocol showed a significant improvement in nurses` knowledge and practice. Recommendations: Nurses are in need for in-service training programs and refreshing courses to improve their knowledge.