Background: Assertiveness is important for effective leadership and team building in nursing. Aim: to investigate the relationship between assertiveness and leadership styles among head nurses. Design: analytic cross-sectional. Setting: the study was carried out at Ain-Shams University Hospitals. Sample: It included all available (98) head nurses. Tools: A Self-administered questionnaire which included two different tools, assertiveness scale and the Multifactor Leadership Questionnaire (MLQ) was used for data collection. Results: The results showed that 77.6% of head nurses‟ had a high level of assertiveness, and high percentages were having transformational and transactional leadership, while less than two-fifth were using passive/avoidant leadership style. Significant positive correlations were revealed between the scores of assertiveness and all domains of transformational leadership, and the contingent reward domain of the transactional style, and negative correlations with passive/ avoidant leadership. Significant positive correlations were shown between the scores of assertiveness and all types of leadership outcomes. Conclusion: The study concludes that head nurses in the study settings have a high level of assertiveness. They mostly use the transformational and transactional leadership styles. Meanwhile, the scores of the transformational leadership domains of idealized influence (attributed), idealized influence (behavior), and inspirational motivation have positive effects on their assertiveness, while the laisser-faire leadership has a negative impact on it. Recommendations: The study recommends training courses for head nurses in certain areas of assertiveness and in situational leadership.