Purpose: The purpose of this study was to investigate the level of self-efficacy, grit (consistency of interest-Cl, perseverance of effort-PE), symptom clusters and self-care agency in brain neoplasm patients and to identify factors influencing their self-care agency. Methods: A descriptive correlational design was used, and the participants were a convenience sample of 152 brain neoplasm patients from C national university hospital in Hwasun. Data were collected using a structured questionnaire from October 1, 2017 to February 15, 2018. The collected data were analyzed using descriptive statistics, t-test, ANOVA, factor analysis, Pearson correlations and multiple regression analysis with the SPSS 22 program. Results: The most frequently reported symptoms included sadness (57.9%), numbness (50.7%), lack of energy (49.3%), nervousness (45.4%), worry (40.8%). There were significant positive correlations between self-care agency and self-efficacy (r=.54, p<.001), Cl (r=.58, p<.001), and PE (r=.50, p<.001). There were significant negative correlations between self-care agency and cluster I (r=-.56, p<.001), cluster II (r=-.31, p<.001), cluster III (r=-.49,p<.001) cluster IV (r=-.30,p<.001). The significant factors influencing self-care agency were self-efficacy, grit, cluster I and cluster IV. These variables explained 55.4% of the variance in self-care agency. Conclusion: The results suggest that intervention programs to increase the level of self-efficacy and grit, to reduce the level of symptoms among patients would improve the self-care agency of brain neoplasms patients.