Smartphone use in the health care settings increased, and there is limited research on the clinical use of these devices by nurses. Aim: Assess effect of smart phone on nursing staff performance in Intensive Care Units at Assiut University Hospitals. Design: Descriptive, correlational design was used. Setting: The study was conducted at Intensive Care Units at Assiut University Hospitals No. = (3 hospitals). Subject: the present study includes a convenient number of nursing staff working in intensive care units at Assiut University Hospitals. (No. = 125). Methods: The data were collected by using I- self-administered questionnaire including, Personal data sheet & Smart phone questionnaire. II- Performance observation checklist. Results: There were low positive effects of smart phone on nursing staff (63.2%), around half of them reported that, they had low perception regarding smart phone applications at work place (42.4%). The majority (92%) of nursing staff were unsatisfied regarding the use of smart phone. Conclusion: The majority of the nursing staff had low perception regarding the smart phone application. Smart phone had low positive effects on them. Almost all of them had unsatisfactory performance as regarding smart phone use. Recommendations: Establish policies to control uses of smart phone among nursing staff at intensive care units. And Provide training program on the appropriate use of smartphones in the clinical setting.