Background : Nurses are one of the parts of the hospital that are in sever need of organizational citizenship behavior due to the necessity for them to complete these jobs, that is influenced by organizational trust. Aim of the study: was to investigate the impact of perceived organizational trust on nurse’s organizational citizenship behavior. Subjects and Methods: Research design: A descriptive correlation design was utilized in this study. Setting: This study was conducted at Zagazig Fever hospital affiliated to ministry of health. Subjects: A convenient sample of 100 staff nurses was used in this study. Tools of data collection: Two tools were used: organizational trust inventory (OTI) and organizational citizenship behavior scale (OCBS). Results: Indicated that the majority of staff nurses had low level of organizational trust (89.0%), while, 90% of them had moderate level of organizational citizenship behavior. Conclusion: organizational trust was positively and significantly correlated with organizational citizenship behavior. Recommendations: Organization should provide the basic needs of nursing staff, establishment of mutual trust among them and themselves and creating a blame-free culture and reward system should be introduced to staff nurses who demonstrate organizational citizenship behaviors.