This study was carried out to find out the Relationship of transformational leadership styles with conscientiousness factors of personality of secondary school administrators in Khyber Pakhtunkhwa, Pakistan. The objectives of the study were to explore the level of conscientiousness factor of personality and transformational leadership style, and to explore the relationship of different sub-factors of conscientiousness factor of personality with transformational leadership style. A sample of 640 school Heads/ Administrators was selected from the population. Stratified random sampling technique was used in the selection of sample. Five Big Factors of personality questionnaire and transformational leadership style questionnaires were used for the purpose of data collection. The questionnaire about the leadership styles was validated through expert opinion and the reliability of the questionnaires used in this study were obtained as a result of the pilot study conducted on 50 respondents. Descriptive statistics viz. mean and standard deviation, Pearson correlation coefficient were used to analyze the collected data. It was concluded from the results of the study that transformational leadership style has significant positive relation with conscientiousness factor of personality and its sub-factors i.e. Self-Efficacy, Orderliness, Dutifulness, Self-discipline, and Cautiousness.