This study aimed to explore the Big Five Factors in the Principal's personality and their relation with his competence in performing his basic and main roles in the Sultanate of Oman. Subjects used in this study were 218 male and female principals, 120 of whom were selected from Muscat Governorate and 98 from Batinah South Region. The scale of the Five Factors personality Scale designed by Costa and McCrae (1992) was used to measure the Five Factors in the principal's personality. In addition a questionnaire was prepared to measure the principal's roles and responsibilities divided into three dimensions: including, Technical, Administrative Human. It was ensured that both the scale and the questionnaire have an acceptable validity and reliability. Concerning the first question, the Means, the Standard deviations, and Repeated Analysis of Variance were employed and the results indicated that there were significant differences among the Big Five factors arranged as follows: extraversion, emotional stability, agreeableness, openness to experience and consciousness. Concerning the second question, the T. test was used and the results showed there was significant difference between males and females in the extraversion experience dimensions, in favor of females. However, there were no significant differences according to the qualification variable in the big five factors, but there were significant differences in the experience variables in three of theses factors. For the third question, the mean and the standard deviation and T. test was calculated for each dimension of the principal's roles and responsibilities (Technical, Administrative and Human) and the results showed there were significant differences between these dimensions. In relation to the fourth question Person Correlation Coefficient was used and the results showed significant relations between the Big Five Factors and principal's roles and responsibilities dimensions in 8 out of 15 correlation coefficients The findings were discussed in terms of literature review and previous studies. Several implications and suggestions for future research were put forward