Background: ICU-AW is considered one of the most important complications occurs in the ICU. Critical care nurses (CCNs) have an important role in the prevention of ICU-AW through applying early mobilization and applying of range of motion exercises. Purpose: The purpose of the study is to examine the leading agents and preventive measures for acquired muscle weakness among Critical Ill Patients. Design: A descriptive exploratory design was utilized to achieve purpose of this study. Setting: the study was carried out in intensive care units Sample: A Purposive sample of seventy-five patients admitted in the previous mentioned setting. Instruments:  Patient assessment tool, muscle strength scale and indicators to incidence of ICU-AW and agents affecting to ICU-AW assessment tool. Results: revealed that, more than half of studied patients had ICU-AW, most studied patients who had muscle weakness were old patients. Administration of corticosteroid and malnutrition was higher in the ICU-AW patients than the Non-ICU-AW patients. There was no statistically significant relation between incidence of ICU-AW and gender, insulin therapy and application of positioning, walking exercises. Conclusion: More than half of studied patients developed ICU-AW. The contributing agents of ICU-AW are patient age, malnutrition, no applying range of motion and chair sitting exercise to ICU patients, administration of corticosteroid. Mobilization as rang of motion exercise and well nutrition is a preventive measures. Recommendations: Further research is recommended to study extensively the effect of nutritional status on incidence of ICU-AW.