The self-confidence of nurses in performing electrocardiographic (ECG) monitoring is a critical competency for managing patients with cardiac conditions in high-acuity settings such as emergency rooms (ERs) and intensive care units (ICUs). This study aimed to identify the factors influencing nurses' confidence in ECG monitoring and to assess their educational needs. A total of 153 ER and ICU nurses participated in this cross-sectional study, completing structured questionnaires assessing their knowledge, confidence, and educational needs regarding ECG monitoring. The findings revealed a moderate mean confidence score of 63.47 (±15.09) out of 100. The key factors associated with higher confidence included the completion of ECG-related education, frequency of evidence searching, and clinical experience within the current department. Additionally, nurses prioritized eight critical educational topics for improving ECG-monitoring competency. These results underscore the importance of tailored educational programs and systematic training strategies to address identified gaps in knowledge and confidence. By prioritizing the specific needs of ER and ICU nurses, healthcare systems can foster supportive work environments, enhance nursing practice, and ultimately improve patient outcomes. Future research should evaluate the long-term impact of educational interventions on nurses' performance and clinical outcomes.