Pre-service teachers rarely receive training on how best to serve lesbian, gay, bisexual, transgender, and queer (LGBTQ) high school students. We tested whether participating in LGBTQ-focused service-based learning or LGBTQ-focused didactic training improved pre-service teachers' knowledge, attitudes, self-efficacy, and skills for serving LGBTQ high school students more than a control group. A non-randomised pre-test-post-test design with eighty-eight participants tested these differences. At post-test, the service-based learning group had significantly higher active-empathic listening and self-efficacy for working with LGBTQ high school students than the control group. There were no differences for didactic versus control groups. Overall, service-based learning may better prepare pre-service teachers to serve LGBTQ high school students.