Gay-Straight Alliances (GSAs) serve lesbian, gay, bisexual, transgender (LGBT) and heterosexual youth from diverse backgrounds. Although some attention has been given to youth members in general, little attention has been given to adult advisors. Among 47 GSA advisors from 33 high schools (39 cisgender female, 8 cisgender male), the authors examined advisors' self-efficacy to address issues pertinent to LGBT youth of color and transgender youth specifically. Advisors' self-efficacy was lower for LGBT youth of color than for transgender youth. LGB advisors reported greater efficacy than did heterosexual advisors to address issues pertinent to transgender youth but not those pertinent to LGBT youth of color. Younger advisors and advisors in schools with a greater proportion of youth of color reported greater efficacy for LGBT youth of color but not for transgender youth. These findings carry implications for ensuring that advisors are equipped to work with GSA-involved youth who may be among the most marginalized in schools.