Dissertation ( MSc. Nursing Education)Background: This study aims to determine the administrative competencies of nurse managers, working in Tertiary Hospitals of Tanzania. Method: this was cross sectional study design with quantitative research approach. Simple randomly sampling was employed to select two zones out of the five zones listed in Tanzania. Purposive sampling method was used to select three public tertiary hospitals and nurse (N=276). Standardized structured questionnaires were used as main data collection tool. Data were analyzed by using Statistical Package for the Social Sciences (SPSS) Version 20. Results: Study revealed that, majority of nurse managers lacked knowledge on administrative competencies. Out of (N=276) nurse managers, 54.3% (N=150) were observed to have poor knowledge on administrative competencies as compared those who had knowledge. Moreover most of nurse managers were observed to have good knowledge in coordinating 71.4% (n=194), followed by planning 22.1 %( n=61) and organizing being the last 17 %( n=48). Nurse manager aged 45+ years old were three times more likely to have a good knowledge on administrative competencies, (AOR=3.297, 95%CI=0.580-4.289, p=<0.05) as compared to other aged groups. Additionally nurse managers with Bachelor and above were four times more likely to have good knowledge on administrative competencies (AOR=3.681, 95% CI=0.045-5.896, p=0.05), as compared with other educational levels. Furthermore nurse manager had working experiences for 21+ years were three times more likely to have good knowledge on administrative competencies (AOR= 3.412,95%CI=1.482, p=0.05) higher than others. Conclusions: it was observed that age, working experience and education level of the nurse managers had positive influence on administrative competencies particularly knowledge. Keywords: Nurse Manager, Administrative competencies, Hospital Management, Planning, Organizing and coordination.