Introduction: Application of nursing guideline of closed suction system had a positive affection critically patient's outcomes, took shorter time and is more economical. Aim of study: was to evaluate the effect of nursing guidelines on patient's outcomes regarding closed suction at intensive care unit. Design: Quasi –experimental research design. Setting, the study was conducted in pediatric intensive care unit at Assuit University hospital. Sample purpose sample 60 critically ill patient's were included in the study. There are categorized into two groups connected with mechanical ventilation who used closed suction from both sex study and control group (30 in each). Tools: three tools developed by the research after review of literatures to assess the patient condition to form baseline data these tool comprised Tool I-patient assessment, tool II-suction assessment, and tool III-outcomes patient tool. Results: The results of the study showed that the effectiveness of nursing guidelines of closed suction system is positive and clear. There was a good improvement of patient's status, the findings of the current study revealed there was significant difference between study and control group regarding to respiratory infection (10) Verus (20), the findings of the current study revealed there was significant difference between study and control group regarding to mortality rate in the study (66.7%) less than control group(93.3%). Conclusion: application of nursing guideline of closed suction system had a positive effect in critically patients out comes. Recommendation Keep the nursing guideline of closed suction system available in all the intensive care units