Primarily,the study aimed to determine the counselors' effectiveness,as rated by their clients and peers among the 50 guidance counselors in the private tertiary institutions in Region VI. Specifically, it tried to ascertain the level of effectiveness of the counselors in the terms of their personal qualities, intervening skills and interpersonal skills when they were grouped according to educational attainment, years of experience,counseling approach,self- efficacy and personality type. Moreover, it attempted to identify the predictors of the guidance counselors' effectiveness. A 40-item research-made Questionnaire on Guidance Counselors Effectiveness (rated by the clients) and a 45-item research-made Questionnaire on Guidance Counselors' Effectiveness (rated by their peers) were used to determine the level of the counselors' effectiveness. To ascertain the level of the counselor's self-efficacy, a 39 -item research-made Self- Efficacy Scale was employed. Myers-Briggs Type Indicator, a standardized personality test was used to find out the counselor's personality type. The mean and standard deviation were employed for descriptive statistics while Mann Whitney, Kruskal-Wallis H Test, Spearman rho, and Multiple Linear Regression Analysis, set vat .05 level of significance were for inferential statistics. The results revealed that the level of the guidance counselors' effectiveness was rated by both their clients and peers very high. They were also rated very high in terms of their personal qualities, intervening skills and interpersonal skills when grouped according to educational attainment,years of experience,counseling approach,self-efficacy and personality type. No significant differences were noted in their level of effectiveness except when grouped according to self-efficacy. A positive significant relationship existed among the personal qualities, intervening skills, and interpersonal skills. However, no variable was determined as a significant predictor of the guidance counselors' effectiveness.