The secondary traumatic stress (STS) of nurses caring for COVID-19 patients is expected to be high, and it can adversely affect patient care. The purpose of this study was to examine the degree of STS of nurses caring for COVID-19 patients, and we identified various factors that influence STS. This study followed a descriptive design. The data of 136 nurses who had provided direct care to COVID-19 patients from 5 September to 26 September 2020 were collected online. Hierarchical regression analysis was conducted to identify the factors influencing STS. Participants experienced moderate levels of STS. The regression model of Model 1 was statistically significant (F = 6.21, p < 0.001), and the significant factors influencing STS were the duration of care for patients with COVID-19 for more than 30 days (β = 0.28, p < 0.001) and working in an undesignated COVID-19 hospital (β = 0.21, p = 0.038). In Model 2, the factor influencing STS was the support of a friend in the category of social support (β = −0.21, p = 0.039). The nurses caring for COVID-19 patients are experiencing a persistent and moderate level of STS. This study can be used as basic data to treat and prevent STS.

Critical reflection develops nurses’ critical thinking and clinical reasoning competency. It is necessary to develop a validated scale to measure critical reflection competency considering the clinical situation and nursing context. Therefore, this study analyzed the concept of critical reflection, developed a scale to measure critical reflection competency, and verified its validity and reliability. The concept of critical reflection and components of the scale were confirmed through literature review and results of previous studies on content analysis. A total of 64 preliminary items were derived on a 5-point Likert scale. The adequacy of vocabulary and expression was checked, and a content validity test was conducted. An I-CVI value of 0.88–1.00 was computed. Construct validity was conducted through an exploratory factor analysis, and data collected from 296 clinical nurses were analyzed. Five factors and nineteen items were derived, and the explanatory power was found to be 53.02%. Cronbach’s α of the scale was 0.853. Future studies need to develop a critical reflection education program and utilize this concept as an educational strategy. We propose a study to verify the effect of applying an educational program using the critical reflection competency scale developed in this study.