As gender-based violence prevention programs around the world increasingly include efforts to engage men and boys as antiviolence allies, both the profound benefits and the inherent complexities of these efforts are emerging. Acknowledging and exploring tensions associated with engaging men is an important element of thoughtfully fostering menÕs antiviolence ally movements so as to both respectfully invite men into antiviolence work and create effective, gender-equitable prevention programming. To this end, this study presents descriptive findings regarding challenges associated with menÕs engagement programming from in-depth interviews with twenty-nine representatives of organizations that engage men and boys in preventing violence against women and girls in Africa, Asia, Europe, Oceania, and North and South America. Programs reported negotiating complex issues related to gender, the intersectional nature of menÕs identities, and establishing legitimacy and sustainability within communities while maintaining ideological focus and consistency. Additionally, programs reported that these tensions manifest across ecological layers of analysis, and impact both the participation of individual men and the programsÕ experiences in community and national contexts.