Through an examination of LGBTQ (Lesbian Gay Bisexual Transgender and Queer) participation in the undocumented immigrant youth movement, this research offers a theoretical framework for understanding how social movements can promote the attainment of leadership roles by members of disadvantaged subgroups contained within a larger constituency. Empirical analyses utilize data from web surveys and semi-structured interviews collected from undocumented youth activists in California in 2011-2012. Findings indicate that LGBTQ activists encountered significant challenges to disclosing their sexual orientation. Yet these youth comprised a significant proportion of movement participants and they were more civically engaged than their straight peers. I argue that LGBTQ prominence among undocumented youth activists can, in part, be attributed to identity processes within this movement. Specifically, the recognition and activation of multiply marginalized identities at various levels of collective identity formation—at the broader movement, organizational, and individual levels—catalyzed intersectional mobilization, meaning high levels of activism and commitment among a disadvantaged subgroup within an already marginalized constituency. At the movement level, I show how the immigrant youth movement’s adoption of the LGBTQ rights “coming out” strategy empowered undocumented youth around both their legal status and sexual orientation. This case of social movement spillover produced a boomerang effect by promoting LGBTQ inclusivity among immigrants. At the organizational level, multi-identity work that addressed activists’ overlapping identities created inclusive environments for LGBTQ members. Finally, at the individual level, LGBTQ undocumented youth exhibited an intersectional consciousness regarding the multiple forms of oppression they experienced; this, in turn, intensified their activism.