INTRODUCTION: Improving physical activity (PA) and healthy eating is critical for primary and secondary prevention of cardiovascular disease (CVD). Behaviour change programmes delivered in sporting clubs can engage men in health behaviour change, but are rarely sustained or scaled-up post trial. Following the success of pilot studies of the Australian Fans in Training (Aussie-FIT) programme, a hybrid effectiveness-implementation trial protocol was developed. This protocol outlines methods to: (1) establish if Aussie-FIT is effective at supporting men with or at risk of CVD to sustain improvements in moderate-to-vigorous PA (primary outcome), diet and physical and psychological health and (2) examine the feasibility and utility of implementation strategies to support programme adoption, implementation and sustainment. METHODS AND ANALYSIS: A pragmatic multistate/territory hybrid type 2 effectiveness-implementation parallel group randomised controlled trial with a 6-month wait list control arm in Australia. 320 men aged 35-75 years with or at risk of CVD will be recruited. Aussie-FIT involves 12 weekly face-to-face sessions including coach-led interactive education workshops and PA delivered in Australian Football League (Western Australia, Northern Territory) and rugby (Queensland) sports club settings. Follow-up measures will be at 3 and 6 months (both groups) and at 12 months to assess maintenance (intervention group only). Implementation outcomes will be reported using the Reach, Effectiveness, Adoption, Implementation, Maintenance framework. ETHICS AND DISSEMINATION: This multisite study has been approved by the lead ethics committees in the lead site's jurisdiction, the South Metropolitan Health Service Human Research Ethics Committee (Reference RGS4254) and the West Australian Aboriginal Health Ethics Committee (HREC1221). Findings will be disseminated at academic conferences, peer-reviewed journals and via presentations and reports to stakeholders, including consumers. Findings will inform a blueprint to support the sustainment and scale-up of Aussie-FIT across diverse Australian settings and populations to benefit men's health. TRIAL REGISTRATION NUMBER: This trial is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12623000437662).