Background: The indwelling urinary catheter (IUC) is a widely utilized device in modern hospital environments, yet they are not always used appropriately in hospital settings and can result in prolonged use and improper management, increasing risk of infections and length of stay. Hence, professional must have knowledge related to the management of urinary catheterization. Aim of the study was to evaluate the impact of protocol of care of patients undergoing urinary catheterization on nurses, knowledge. Subjects and Method: A quasi- experimental research design was used to conduct this study. The study was carried out at Intensive Care Unit, Urology Department and Department of Internal Medicine at Al-Azhar University hospital in Damietta City to test the hypotheses that positive changes in nurses' knowledge after implementing the protocol of care for patients undergoing urinary catheterization. A convenient sample of 50 nurses was included. One tool was used for data collections, part (1) Structured Interview Questionnaire tool that includes demographic data part (2) Nurse's Knowledge Assessment tool, to assess nurse's Knowledge about urinary catheterization and urinary catheter care Results: demonstrated that there were statistically significant improvements in the total score of nurses' knowledge regarding care of patients undergoing urinary catheterization throughout the protocol intervention . Recommendations: The study recommended that providing ongoing in-service education for nurses to update their knowledge related to care of patients undergoing urinary catheterization and catheter –associated problems.