Background: Nurse managers leadership style is especially important to enhance staff nurses commitment which fulfill helping organizational objectives. Aim: the aim of this study was to identify the effect of nurse managers' leadership styles on staff nurses' organizational commitment through: assessing different styles of leadership among nurse managers, determining level of organizational commitment among staff nurses and finding out the effect of nurse managers' leadership styles on staff nurses' organizational commitment.Study setting: this study was carried out at Nasser Institute Hospital. Study design: this descriptive correlational design. Study subjects: the study was carried out on 80 nurse managers, and 174 of their staff nurses in the hospital setting. Tools of data collection: Two tools were used to collect data namely, leadership style questionnaire and organizational commitment questionnaire. Results: the democratic leadership style was the most highly used by (63.8%) of nurse managers and (54.6%) of staff nurses had high total commitment level. Conclusion: The study concluded that the nurse managers' democratic leadership score is a positive predictor of staff nurses' commitment, while the autocratic style score is a negative predictor. Furthermore, the study recommends that frequent regular meetings between nurse managers and their staff nurses to discuss nurses work problems and recovered their problems for better relationships and enhances support at work with suitable rewards for staff nurses.