The purpose of this study was to assess and describe the practiceof principals’ leadership styles and teachers’ organizational commitment at government and private secondary schools in Mekelle Administrative zone of Tigray Region. Four research questions related to practiceof principals’ leadership styles and teachers’ organizational commitment were formulated to guide the study. In order to answer the research questions descriptive survey research design was employed. The data was collected in 12 secondary schools from which 7 of them were government schools and the remaining 5 schools were Private schools. From these sample schools 120 teachers, 120 students, and 29 principals were selected by multistage stratified sampling. Data from the participants was collected using questionnaires and FGD guiding questions. The data obtained from the above sources were analyzed by using both descriptive and inferential statistical methods. The major descriptive statistics used were frequency count, percentage, mean, and standard deviation and the major inferential statistical used was independent sample t-test and Pearson correlation. The results of the study revealed that Majority of teachers and students taken from both government and private schools and participated in this research perceived that generally their principals have more frequently exercised transactional leadership style than transformational leadership style even though government school principals exercised transformational leadership style in somewhat better frequency than their counterpart private school principals. The analysis has also shown that from different kind of transformational leadership styles Idealized Influence and Inspirational Motivation styles were practiced more frequently than Individualized Consideration and Intellectual Stimulation in government schools. Generally the practiced leadership style and the teachers’ commitment level were found to be weakly correlated nevertheless its correlation was positive. This indicates that teachers’ commitment is a multivariate issue that could be influenced by other factors other than practices of leadership style. From the above findings, the conclusion drawn was that the dominant leadership style practiced in both government and private secondary schools of mekele zone was transactional leadership style. Government schools teachers’ commitment was found to be lower than private schools. Based on the findings of the study and the conclusions drawn, the recommendations were forwarded to improve school leadership style practices for betterment of teachers’ commitment level of mekele zone secondary schools in particular and other school leadership practice in all school in general.