Purpose: : This study aimed to investigate the impact of clinical reasoning competence, positive psychological capital, and nursing work environment on nursing performance of intensive care unit (ICU) nurses in tertiary general hospitals. Methods: : Data were collected from 169 ICU nurses in tertiary general hospitals in Busan, South Korea, from July 27 to August 15, 2023, using a self-report questionnaire. After excluding 12 questionnaires with insufficient responses, 157 responses were analyzed. Descriptive statistics, independent t-test, one-way ANOVA, Pearson’s correlation coefficient, and stepwise multiple regression analysis were employed. Results: : Factors influencing nursing performance included clinical reasoning competence (β=.51, p ＜.001), hope as a subfactor of positive psychological capital (β=.31, p ＜.001), and the nursing foundations for quality of care in the nursing work environment (β=.21, p ＜.001). The explanatory power of the regression model was 62% (F=87.41, p ＜ .001). Conclusion : The study underscores the importance of improving clinical reasoning competence among ICU nurses to enhance nursing performance and foster a hopeful attitude through reflective practices and personal growth. Organizational interventions, such as educational and psychological support programs, along with creating a supportive nursing environment, are crucial for improving nursing performance among intensive care unit nurses.