Institutions of higher education strive to create a diverse, inclusive, and civically engaged student body. Encouraging students to critically engage in social justice enhances the ability of universities to achieve these desired outcomes and empirical studies link activism to greater gains in civic engagement and democratic ideas later in life (Mayhew, Bowman, Rockenbach, Seifert, & Wolniak, 2016; Pascarella & Terenzini, 2005). Advocacy and allyship provide avenues of participation for students to critically engage in social justice and subsequently practice civic engagement through aligning their values and actions. "Advocacy" is the process of taking actions to end oppression of one's own marginalized group, while "allyship" is the process of taking actions to end oppression of another marginalized group with in which a person does not have membership. While previous scholarship addresses the development of social justice values, there is relatively little empirical research that addresses the process of translating these values into social justice activism. The small literature base that does address the process of social justice activism for college students does not give attention toward understanding how students develop a commitment to both advocacy "and" allyship. Thus, this study fills a gap in the literature. Through using a constructivist grounded theory approach, I developed a substantive theory that addresses the process by which undergraduate college students with one or more marginalized identities engage in both advocacy and allyship. To create my substantive theory of advocacy and allyship, I used the technique of theoretical sampling to conduct two rounds of interviews with ten participants and collected observational data. In keeping with grounded theory methods, I immersed myself in the data while simultaneously analyzing it. Participants in this study attended one of two large public universities in the Southeast, held at least one marginalized identity, and took actions that related to both advocacy and allyship. I conclude that advocacy and allyship is a continual and evolving process in which college student activists consistently return to "Doing the Right Something," the core category of this process. The process of advocacy and allyship consists of six additional categories: "Becoming Aware," "Educating Self," "Exploring Beliefs about Advocacy and Allyship," "Navigating Different Viewpoints," "Feeling Connected," and "Experiencing Affirmation." Additionally, "Sociopolitical Climate" and "Identity" represent two influencing factors that affect and shape the process of advocacy and allyship. A substantive theory holds both theoretical and practical implications. My substantive theory of advocacy and allyship enhances the theoretical understanding of intersectional identity development, Critical Consciousness Theory, and in-group activist and ally development. In addition, my substantive theory on advocacy and allyship offers practical relevance for student affairs professionals who support students as they engage in advocacy and allyship on college campuses and as they encourage the student body to align their social justice values to action. Finally, my substantive theory of advocacy and allyship holds pedagogical relevance for graduate student affairs programs and helps inform structural changes that may increase activism on campus. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]