Introduction: Years ago there were an idea that pay is the most important cause of work motivation. Later, researchers found that the design and the characteristics of the job greatly affect the employee motivation. Aims: Identify the extent to which the nurse's job have skill variety, task identity, task significance, autonomy and feedback, assess the nurses internal work motivation, and find the effect of job characteristics on nurses internal work motivation. Study design: A descriptive correlational design was used. Setting: The study was conducted at Main Assuit University Hospital. Subject and Method: The subject of the study was all bedside nurses working in the Intensive Care Units at Main Assuit University Hospital (159). A self – administered questionnaire was used to collect data which includes: Personal data sheet, Work Design Questionnaire, and Multimethod Job Design Questionnaire. Results: Autonomy and Feedback correlated positively and significantly with motivation. Conclusion: Activities performed by nurses have high skill variety, task identity, task significance, autonomy and feedback and high internal work motivation, also the most effective core job characteristics on motivation were autonomy and feedback. Recommendations: organizations system should include information about the importance of job characteristics in improving nurses' satisfaction, motivation and quality of care.