This study was conducted to investigate transformational leadership style of principals in human resource management in public secondary schools in South East Nigeria. The study was guided by four research questions with four corresponding null hypotheses formulated. Literature relevant to the study was reviewed. Descriptive survey research design was adopted for the study. The population of the study consisted of 25, 220 principals and teachers in 1,244 public secondary schools in the five South East states of Nigeria, out of which 1, 250 comprising 1000 teachers and 250 principals, were sampled using proportionate stratified random sampling technique. A structured questionnaire titled Transformational Leadership Style of Principals and Human Resource Management Questionnaire. (TLSPHRMQ) with reliability of 0.95 was used for data collection. 1,250 copies of the questionnaire were distributed and 1,233 were returned. Data collected were analyzed using mean and standard deviations to answer the research questions, while t-test statistics was used to test the null hypothesis at .05 level of significance. The results indicated that principals of public secondary schools in South East Nigeria fairly (great extent) adopt transformational leadership style, sometimes (little extent) adopt transactional leadership style and once in a while (very little extent) adopt laizzez faire leadership style. It was also found that the principals adopt transformational leadership style and staff development, staff motivation and staff discipline to a great extent. The null hypotheses tested showed that there is no significant difference between the mean ratings of principals and teachers on leadership styles of principals, there is no significant difference between the mean ratings of principals and teachers on the extent principals adopt transformational leadership in staff discipline. Other findings include; there is significant difference between the mean ratings of principals and teachers on the extent principals adopt transformational leaderships style in staff development and that there is significant difference between the mean rating of principals and teachers on the extent principals adopt transformational leadership style in staff motivation. Based on the findings, the researcher recommended among others that school board of different states in South East Nigeria who are responsible for appointing new principals should make it a point of duty to train them in transformational leadership style, and that educational policy makers on their part should make a policy for in-service training of principals in transformational leadership practices, so that those principals who are already making use of transformational leadership style in their different schools will be encouraged.