Background: Patients' safety is fundamental to the provision of health care in all settings. However, avoidable adverse events, errors and risks associated with health care remain major challenges for patient safety globally. Aim of study: This study aimed to evaluate the effect of implementing nursing care protocol on critical patients' safety outcomes. Design: A quasi experimental - design was utilized to achieve the aim of this study. Setting: This study was conducted at the general intensive care unit at Benha University Hospital. Subjects: Convenience sample of all available nurses (63 nurses) who are working in Intensive Care Unit (ICU) & a convenience sample of 60 consecutive eligible patients who attended to ICU within 6 months. Tools of data collection:     Data of the present study was collected by using the following three tools. I: Structured Questionnaire for nurses. II: Patient safety practices observational checklist and III: Patients ' safety outcomes checklist.  Results: The post mean knowledge and practice scores of nurses regard patients' safety post nursing care protocol implementation were higher than pre implementation, there is a highly significant positive correlation between total nurses' knowledge and their practice at pre and post implementation of nursing care protocol where p < 0. 001. Conclusion: There was an improvement in patient' safety outcomes for study group than control group after one week with statistically significance difference. Recommendation: In service education should provide in hospital to improve nurses' performance regarding patient safety measures through acquiring knowledge and through implementing the established standards of care which must be updated periodically.