Background: Significant health disparities exist for sexual minority youth (SMY). While supportive adults in schools have been shown to improve mental wellbeing and academic outcomes for students, most teachers do not receive training specific to lesbian, gay, bisexual, transgender and queer or questioning (LGBTQ) students. Methods: The project aimed at providing staff from a Hawaii middle school with "Safe Space" professional training to increase knowledge and comfort in supporting SMY. Pre- and post-training surveys were used to measure knowledge of LGBTQ issues and comfort in supporting LGBTQ students and a 2-week and 3-month survey assessed staff's application of newly learned material. Results: Sixty-four staff participated in the first of 2 training sessions with 59 completing both sessions. Results from the pre- and post-survey showed a 34.9% increase in knowledge of LGBTQ issues (effect size = 1.22) and a 5.5% increase in self-rated comfort level in supporting LGBTQ students (effect size = 0.22). A 3-month follow-up indicated that 52.9% of the respondents were actively applying knowledge learned within their school setting. Conclusions: The project results demonstrate the value of the training not only in the short term but also staff's ability to apply the knowledge they learned. Given the success of implementation, expansion to other schools could facilitate ally-building attitudes and behaviors as a protective factor for SMY throughout the state.