In this descriptive study, we aimed to identify factors related to emergency room nurses’ disaster triage ability. A total of 166 nurses who worked for emergency departments of general hospitals completed a structured questionnaire consisting of the Disaster Triage Ability Scale (DTAS), the Strategic Thinking Scale (STS), the Problem-Solving Inventory (PSI), and the Original Grit Scale (Grit-O). The data were analyzed using SPSS/WIN 25.0 by means of descriptive statistics, t-test, one-way ANOVA, the Scheffé post hoc test, Pearson’s correlation coefficients, and stepwise multiple regression. Participants’ DTAS averaged 14.03 ± 4.28 (Range 0–20) and showed a statistically significant difference according to their experience of triage education (t = 2.26, p = 0.022) as a disaster triage-related attribute. There were significant correlations among DTAS and confidence in the PSI (r = 0.30, p < 0.001), the approach-avoidance style in the PSI (r = −0.28, p < 0.001), and futurism in the STS (r = 0.19, p = 0.019). The strongest predictor was confidence in the PSI; in addition, 14.1% of the DTAS was explained by confidence in the PSI, approach-avoidance in the PSI, and futurism in the STS. Emergency room nurses who received triage education showed a higher level of the DTAS and their DTAS could be explained by problem-solving skills and strategic thinking. Therefore, it is necessary to develop and implement triage education programs integrated with stress management to improve the approach-avoidance style to ensure better problem-solving skills and to utilize various training methods to enhance confidence to improve problem-solving skills and futurism as part of strategic thinking.