The purpose of this explanatory research project is to examine the role of leadership style in the organizational change effectiveness at ECX. A structured questionnaire was prepared to measure the role of leadership styles (independent variable) on the organizational change effectiveness (dependent variable). Primary and secondary data sources were used. Questionnaire and interviews were data collection methods. Both quantitative and qualitative research approaches were implemented and the research questions were also examined on a sample of 147 staff of ECX at the Head Office in Addis Ababa. Out of the 147 distributed questionnaires, valid response was collected from 111 respondents. The data were analyzed using descriptive statistics, correlation analysis to identify any relationship between the variables & regression analysis to predict the change in the dependent variable when the independent variables change. The result showed that the Transformational Leadership Style is predominantly practiced at ECX followed by the Transactional Leadership Style with high and moderate correlation coefficients respectively. Laissez-faire leadership style has positive but weak correlation with the Organizational Change Effectiveness. The independent variables are also found to be good predictors of the dependent variable. Furthermore, the Transformational and Transactional Leadership Styles are found to be statistically significant predictors of the Organizational Change Effectiveness while Laissez-faire is not. Based on the findings and conclusion, the researcher recommended that top management should give more emphasis to the Transformational Leadership Style as it was found as the dominant leadership style at ECX currently which also found to have a strong positive correlation with the Organizational Change Effectiveness. This dominant leadership style was also found to be statistically significant predictor of the Organizational Change Effectiveness