Purpose: This study was conducted to investigate the level of nursing professionalism and the factors affecting it, In addition, it can serve as a fundamental resource for development of appropriate strategies for nursing professionalism. Method: This study was performed on 370 nurses working at two university hospitals located in Seoul. Data was analyzed by Pearson correlation analysis, and stepwise multiple regression using SPSS Win 14.0. Result: The estimated regression model of nursing professionalism was statistically significant (F=199.89, p=.000). Major factors influencing nursing professionalism were observed as ability of job performance (${eta}=.811$), job satisfaction (${eta}=.140$), organizational commitment (${eta}=.086$), and turnover intention (${eta}=.084$). These four factors explained 67.9% of nursing professionalism. Conclusion: Based on the results of the study, further research is needed to investigate other factors affecting nursing professionalism.