Introduction: The need to determine the factors affecting nurse competency is to assist determine practical approaches to enhance competency. Aim: The study aims to map the competencies of emergency department (ED) nurses, its influencing factors, and barriers. Subjects and Methods: This study employed a cross-sectional approach conducted at the government hospitals in Hail, including village hospitals. The participants of this study were the 227 ED nurses as a result of convenience sampling. The researchers utilized the Google Form survey to collect the data. The data collection was conducted between August and September 2022. Results: Nurses in this study were highly competent (227/275). Clinical care competency has emerged as the highest competency (3.79 ± 0.646), followed by leadership (3.53 ± 1.053). Those who are 26–30 years old (B = 0.766; P < 0.000); 95% confidence interval (CI) (0.623–0.909) are far better than the other age groups. Furthermore, 5 years and above were competent compared to those with <5 years of experience (B = −1.135; P < 0.000; 95% CI [−1.271–0.998]). Moreover, those who have training in the ED (B = 1.127; P < 0.000; 95% CI [0.588 ± 1.666]) have better competencies than those who have no training in ED. Barriers were that the training was not in line with the ED nurses' needs and lack of leaders' support (92.5%). Conclusion: The ED nurses were highly competent, especially in the clinical care leadership competency. The older age group and <5 years of experience and training with ED were influential to their competency. Barriers were that the training was not in line with the needs of the ED nurses and lack of support from leaders. Study findings suggest that the measurement of competency be continuous to improve the competency of the ED nurses. Training needs assessment specifically in the ED, to be conducted periodically and offer continuous nursing education based on the identified needs of the nurses