Aim: This study aimed to evaluate effects of patient deterioration early warning score system simulation training on nurses' performance, satisfaction and self-confidence. Methods: Convenience sample of 40 nurses working in Dawadmi general hospital and willing to participate in the study was included. A Quasi experimental research design pre/post intervention was used. Four tools were used in his study; First tool used to assess nurses' demographic characteristics & their knowledge regarding early warning score system. Second tool used to assess nurses' practice regarding clinical deterioration to safe patients'' life. Third tool nurses' satisfaction scale this tool; used to assess nurses' satisfaction to use early warning score system simulation for deteriorated patient. Fourth tool; nurses' selfconfidence scale to assess studied nurses' self-confidence in their abilities to using early warning score system simulation for caring of deteriorated patient. Results: Studied nurses' total score of knowledge reflect highly significant differences pre and post intervention. Nurses' practice was improved significantly post the intervention; where half of them take good total score in using Early warning scoring system simulation to care for patients post intervention compared with none of them pre and their satisfaction to use early warning score system was improved significantly post intervention with statistical difference was found. There was highly statistical significant difference regarding nurses' self-confidence pre/post intervention Conclusion: nurses' practice was improved significantly post the intervention with statistical difference was found. Also nurses ' satisfaction and their self-confidence to use early warning score in caring for deteriorated patients was improved significantly post compared to pre intervention