Background: Assertiveness is an invaluable component for successful professional practice in order to curb absenteeism in the workplace and encouraging for career development and achieve organizational goals. Aim: The study aimed to assess assertiveness levels and absenteeism causes and their relation to career development factors among nursing personnel at Benha University Hospital. Design: descriptive correlational research design. Setting: The study was conducted at Benha University Hospital. Subjects: Simple random sample consisted of 450 staff nurses and convenient sample consisted of 150 nursing management staff. Tools: Data of this study were conducted by using three modified tools: (a) Assertiveness questionnaire (6) items (b) Absenteeism questionnaire (7) items (c) Career Development questionnaire (5) items. The results: of the present study revealed that majority of studied nursing personnel had high levels of assertiveness, the highest percent of them agreed about “self fulfillment' was the most important causes contributed to nursing absenteeism followed by relationships among staff nursing, the highest percent of them agreed about “work support" was major factor assisted career development. Conclusion: that there was significant positive relation between assertiveness levels and absenteeism causes, also there was significant positive relation between assertiveness levels and career development factors. Recommendation: mainly management & leadership training program for the supervisors to improve skills and reduce absenteeism with providing strategies necessary for career development.