Background and Objective: Due to the health care system's complexity, the demand for effective leadership in nursing has never been so great. The need for studies of variation in leadership styles that could assist nursing leadership in fulfilling their administrative responsibilities is emphasized. The aim of the study was to investigate the head nurses' leadership styles and effectiveness, flexibility and adaptability of styles in self-report and reports by staff in the hospital setting in 2010.Materials and Methods: This study used a descriptive–analytical design. The instruments used was "Leader Effectiveness Adaptability Description (LEAD-self and LEAD-other)" standard questionnaire. The questionnaire was returned by 330 including 42 head nurse and 288 staffs who were working in educational hospitals in Arak city. They studied a census method. Data were analyzed using SPSS (13) and descriptive-analytical statistics. Results: It was found out that 73/8% of head nurses were female, 88/1% married, 35/7% aged 35 to 40 years and 40/5% had a history of serving 10 to 15 years. Also, 95/8% of nurses were female, 51/4% married, 42% aged 26 to 30 years and 57/3% had served less than five years. Results indicated HNs and staffs rated "coaching" as most prevalent leadership style. Effective leadership style from the highest viewpoints of both was selected yet high adaptability with the lowest amount and low flexibility in "delegating" leadership style with highest amount were determined.Conclusion: Effective leadership style with low adaptability and flexibility was outcome of leadership performance evaluation led by head teaching hospitals in Arak. The results of this study provide guidelines for management development programs, training, and career planning for HNs. Educating the HNs on situational leadership style is recommended. This educational program should focus on the role of leadership in managerial process and effectiveness.