Abstract: This study investigated Principal Personal Variables as determinant of administrative effectiveness and efficiency using descriptive design of correlation type. Three hundred principals selected through simple random sampling technique from secondary schools in Ogun State participated in this study. The researcher developed and validated questionnaires tagged Leaders Personal Variable Questionnaire (LPVQ) and Personal Effectiveness Scale (PES) for data collection. The Multiple Regression and Analysis of Variance (ANOVA) were the major tools used for data analysis. Findings from the study revealed that a low, positive correlation (R = 0.20) exists between the four predictor variables (age, sex, experience, qualification) and principal personal effectiveness. It was recommended among others that principalsοΏ½ and head of schools should be subjected to regular training and workshops boost their effectiveness and efficiency. The principalsοΏ½ personal variables of experience and qualification should be one of the factors in appointing teachers to position of authorities in schools.