School counselors who engage in advocacy work may experience barriers when attempting to challenge oppression; hence, they need specific skills to advocate efficiently and effectively. Despite the trend in conceptual articles surrounding school counselor advocacy, little is known about how school counselors' multicultural self-efficacy predicts school counselors' social justice advocacy practices. This study addressed this gap in the literature by exploring factors related to school counselor social justice advocacy; that is, multicultural self-efficacy. Multicultural self-efficacy and advocacy competence have had an integral role in fostering school counselors' abilities to identify and support the needs of diverse student populations within the K-12 educational system. Using Bandura's social cognitive theory as a framework, this study examined perceptions of school counselor multicultural self-efficacy and social justice advocacy competency. The School Counselor Multicultural Self Efficacy Scale (SCMES) and the School Counselor Advocacy Assessment was administered to a national sample of school counselors. The sample consisted of 180 participants who met the inclusion criteria. Multivariate multiple regression and repeated measures multivariate analysis of variance were used to test the hypotheses. The results showed that SCMES subscales of school counselor multicultural self-efficacy are statistically significant predictors of school counselor social justice advocacy. Social change implications including areas of focus school counselor educators can embed in social justice advocacy as part of multicultural counseling competence and an ethical mandate in the profession are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]