Purpose: The purpose of this study was to identify the factors influencing nursing performance after analyzing the relationship between grit, clinical decision making, and nursing performance perceived by nurses in medium-sized hospitals. Methods: This study adopted a descriptive cross-sectional approach. Data were collected from 140 nurses who were conveniently sampled and over six months of working at four medium-sized hospitals in G city. The data were collected using structured questionnaires. The data were analyzed with SPSS 26 which was used for descriptive statistics, independent t-tests, one-way ANOVA, Pearson’s correlation, and multiple linear regression. Results: The participants’ level of grit averaged 2.87±0.32 out of 4 points, the level of clinical decision making averaged 3.28±0.23 out of 5 points. Nursing performance had an average score of 3.66±0.50 out of 5 points. There were significant positive relationships between grit (r=.48 p<.001), clinical decision making (r=.33, p<.001) and nursing performance. Significant factor was grit that explained 25% of nursing performance. Conclusion: This finding presented that grit is a variable influencing nursing performance in medium-sized hospitals, providing evidence for developing strategies to enhance nursing performance. Therefore, providing programs that enhance the subcomponents of grit-such as persistence to achieve long term goals, the passion to become a nursing professional, and patient oriented intrinsic motivation-may lead to improved nursing performance.