Background: Performing physical activity on a regular basis and having proper health behaviors can bring many benefits to staff nurses as improving their job performance with having more energy to complete the work allocated to them which affect positively on the quality of patient care. Aim of this study was to explore the effect of physical activity and health behavior on staff nurses' job performance. Methods: Design: Descriptive - cross sectional research design was used. Subjects: The study included representative sample (35%) from all staff nurses (314) working at Tanta Emergency Hospital and the total sample was (110) of staff nurses. Tools: Three tools for data collection were used. Tool (I): Physical Activity Questionnaire. Tool (II): Health Behavior Assessment Scale. Tool (III): Staff Nurses' Job Performance Observation Checklist. Results: High percent (77.3%) of staff nurses had low level of physical activity and 69.1% and 45.5%of them had moderate level of health behavior and job performance respectively. Conclusion: It was concluded that significant positive correlation between staff nurses' job performance with physical activity and health behavior. Recommendations: Hospital administrators need to hold in service education programs on healthy behaviors and physical activity to promote nurses' health and ensure raising level of their performance.