Nurses require greater autonomy and participation in decision making, nurse participation in decision making in an organization varies depending on many factors, including the influence of nurse manager leadership and collaboration with physicians. Aim. The aim of the current study was to assess dominant leadership styles , level of decision making autonomy among critical care nurses and relationship between leadership style and decision making autonomy. Design. A descriptive cross-sectional correlation research design was utilized in this research. Setting .The current study was carried out at two hospitals' namely; King Fahd Hospital of the University (KFHU) in Saudi Arabia and at Tanta Main University Hospital in Egypt in Intensive Care Units (ICUs). Subjects. The study subjects encompassed all full time nursing staff convenient sample in previous settings (n = 27) Head nurses 16 from Egypt, 11 from KSA, and Critical Care nurses ( n= 74 ) divided as the following ; 35 from Egypt and 39 from KSA . Tools. Two tools were used in this study. Tool I. It was structured questionnaire , assessed decision making autonomy . It included two parts ; part one was demographic data (7 items), part two was autonomy issue (18 items). The autonomy domain comprised 18 items ( knowledge 6, action 6, value 6 ). Tool II Assessed leadership styles , it included two parts ;part one was demographic data (6 items) ; age, sex, experience (general and specific in the unit), last education, type of hospital, type of unit , part two: Leadership styles Questionnaire this questionnaire was designed to measure three common styles of leadership: authoritarian, democratic, and laissez -fair. It composed of 18 statements. The respondents were presented with a five point likert scale, the number indicates the degree to which the respondents agree or disagree (5-1). Results. In KSA studied nurses had the highest mean score. for total autonomy scale. A s well as, there are statistical significant difference for two bases of autonomy knowledge, and action bases also total autonomy. Conclusion. Overall, results of the present study revealed head nurses applied situational leadership theory in both countries. As well as, in KSA nurses had higher decision making autonomy than nurses in Egypt. Recommendation. ICU nurse managers should foster nurses' autonomy by enabling them to exercise clinical decision-making, and Actively supporting nursing decisions and nursing accountability.