Men’s violence against women includes acquaintance rape, intimate partner violence, sexual assault, and partner stalking and occurs at particularly high rates on college campuses (Fisher, Cullen, & Turner, 2000). Although men are increasingly becoming involved in efforts to prevent these forms of violence, little is known about their motivation and the processes that lead to their involvement. The purpose of this project was to examine how undergraduate male students become social justice allies involved in preventing men’s violence against women. The theoretical frameworks of this study included transformative learning theory (Mezirow, 1997, 2000) and feminist theory (Worell & Remer, 2003). Data were generated from six male social justice ally exemplars nominated for their sustained involvement in prevention work. Eligible and interested participants completed two individual interviews, demographic forms, Social Locations Worksheets (Worell & Remer, 2003), and male social justice ally development timelines. The qualitative data were analyzed using constructivist grounded theory (Charmaz, 2006) by the author and three peer debriefers. Findings provide an initial framework for conceptualizing male social justice ally development, including predisposing factors and shifts in perspective that were critical to their antiviolence work and factors that sustained their involvement. Participants also described integrating their social justice ally work into their identity and connecting with other forms of social activism. These themes provide a framework for understanding how men become invested in preventing men’s violence against women as undergraduate students and implications for ways to engage more men in these efforts.