Introduction: In postindustrial age, knowledge management is the newest management approach that knowledge workers are the essential in organizations so their retention and productivity are the important challenges in human resource management. Also, hospitals are as a knowledge and expertized organization that the majority of personnel are nurses who are knowledge workers that their retention is very important for them.

Aim: The aim of this study was assessing the effective factors on retention nurses as knowledge workers in hospitals.

Method: This study was an applied descriptive study that was done   in 2011-2012. By stratified sampling, 388 nurses who worked in teaching hospitals of Tehran university of Medical Sciences were selected randomly. Data were gathered by researcher made questionnaire that it had 52 questions. They assessed statuesque , desirable situation and effective factors(personal, organizational and job). Its reliability was 95% for statuesque and 97% for desirable situation and also content validity was attained by expertized faculty member. Data Analysis was done by dependent t test and Friedman test by SPSS software.

Results: Data analyzing showed that effective factors on retention of nurses as a knowledge workers in status currenr and desired situation were as follows ranked. The first priority factor was organizational factors (corporation, motivation, organizational communication, and education and performance management). And then personal factors (power and skill, job satisfaction, competency) as a second priority and finally job factors (meaningfully and challenging of work, freedom, Authority and role clarity) was the latest.

Conclusion: It is recommended that hospitals improve necessary conditions for   corporation, motivation, organizational communication, and education for nurses. In addition, it is recommended to nurses who are knowledge worker improve their individual skills and team-work capabilities to increase their competence and job satisfaction.