The purpose of this study was to identify the related factors of patient safety competence of nurses. The data was collected from 238 nurses in two different university hospitals and three general hospitals in B metropolitan city and Y city. Patient safety culture of nurse was measured by a tool by the US’ Agency for Healthcare Research and Quality (2004) and then translated by Kim Jung-eun et al. (2007) into Korean. Self-leadership was measured by Manz (1983) and then translated by Kim Han-seong (2002), and patient safety competence was measured by Schnall et al. (2008) and then modified and complemented by Lee et al. (2014). The collected data was analyzed by descriptive statistics, t-test, ANOVA, and multiple regression. Factors influencing patient safety competence were self-leadership and patient safety culture. Based on the results, it is necessary to improve nurse’s patient safety competence various educational programs for enhancing self-leadership and creation of patient safety culture by raising awareness of patient safety in those involved in medicine.