Bullying varies in frequency, intensity, duration and hence severity, and contributes uniquely and directly to mental health problems, with severe and long-lasting consequences. Almost a half of school-age students report being bullied in the past year. All school staff, especially school counsellors, are uniquely positioned to reduce student bullying through proactive primary prevention, early intervention, and treatment. However, given the intensity of schools, and counsellors' limited time and resources, robust evidence is needed to guide their unique contribution to a whole-school approach to reducing bullying behaviour. Since 1999, a pipeline of 18 Friendly Schools studies, including seven randomised control trials, have developed and tested ways to build all school staff's capacity to effectively target and deliver evidence-based strategies across the prevention, early intervention and treatment continuum to reduce harm from all forms of bullying behaviour. This article describes the implications of Friendly Schools' research findings relevant and applicable to the work of school counsellors, as part of a whole-school approach to bullying prevention. These implications demonstrate the interconnectedness of actions of all members of the school community, and the need for a whole-school commitment to preventing and reducing bullying, to realise the important synergistic contribution of school counsellors.