Purpose: This study was conducted to provide basic data for quality improvement among oncology advanced practice nurses (oncology APNs) through increasing job satisfaction by determining their job satisfaction level and analyzing the influencing factors. Methods: The subjects were 114 certified oncology APNs working at general hospitals in metropolitan areas. Data were collected using a structured questionnaire from August 4 to October 29, 2018. The instruments were the Role Conflict Scale, Self-Efficacy Scale, Professional Self-Concept Scale, and the Level of Job Satisfaction. The data were analyzed using descriptive statistics, t-tests, chi-square tests, ANOVA, Pearson's correlation coefficients and multiple regression in SPSS version 23.0, IBM. Results: Factors that significantly affected job satisfaction were number of years since being certified as an oncology APN (β=-.20, p=.031), oncology advanced practice (β=.38, p<.001), and professional self-concept (β=.44, p<.001). The explanatory power was 39.4%. Conclusion: These results showed that factors significantly affecting job satisfaction were number of years since being certified as an oncology APN, advanced practice in oncology, and professional self-concept. Job satisfaction was found to be higher when the number of years since being certified as an oncology APN was shorter and professional self-concept was higher. [ABSTRACT FROM AUTHOR]