This paper reports on aspects of an Australian study into the factors and conditions that make it possible for secondary school health education teachers to include and affirm gender and sexual diversity in their teaching. The study examined the impact of a two-day intervention designed to prepare teachers to use a major new government-funded teaching and learning resource called Talking Sexual Health. The study found that whilst there was a range of personal and structural barriers inhibiting change, professional development and access to teaching and learning resources could indeed impact positively on teachers' willingness and ability to include and affirm diverse sexualities in their health education programs.