Background: First-line nurse managers core competencies are essential skills, abilities, and behaviors needed to be effective managers. Aim: Assess first line nurse managers core competencies. Subjects and method:  Design: Descriptive design Setting: This study was carried in Port-Said hospital, Port-Foad hospital, EL-Zhour hospital, and El-Nasr hospital. Subjects: included all first line nurse managers presented in four hospitals at the time of data collection. Tool: Structured questionnaire consisted of two parts: the first part included the demographic data, and second part is first line nurse managers core competencies questionnaire. Results: the study revealed that the highest total score was regarding to frequency of application ( = 87.9, SD = ± 4.0), the highest frequent skills were related to both management skills, teaching skills ( = 88.3, SD = ± 22.6). Following the importance of core competencies' application, the greatest important reported skills were the leadership skills ( = 86.6, SD = ± 10.2), critical thinking skills ( = 85.4, SD = ±9.6).Conclusion: all studied first line nurse managers self-assessed their frequency, and importance of application of core competencies as high. They reported that the most applied core competencies were management skills followed by teaching skills, the most important core competencies were leadership skills, flowed by critical thinking skills; and there is no significant relation between total score of frequency and importance of application of core competencies skills and any demographic data. Recommendations: Implemented to assess (FLNMs) core competencies from the perspective of their subordinate, top managers.