Despite the increasing appeal of community sport programmes which focus on men's mental health, the key design characteristics of these programmes, and the roles played by delivery staff in their conception and development, have not yet been systematically or widely studied. In this qualitative paper we address this gap in knowledge by reporting on interviews with stakeholders (n = 18) from north-west of England involved in designing a men's rugby league community-based mental health programme, Offload. Findings suggest that tacit forms of knowledge, developed through years of professional practice and co-production activity, was critical to how men's mental health was conceptualised and the use of existing non-clinical community assets (e.g. professional club stadia) as delivery sites for the programme. The use of non-stigmatising language, supported by opportunities for men to engage in non-threatening and solutions-focused activities, were central to programme design. The use of former professional sportspeople who recall their own lived experience of mental illness, and personal adversity, in programme sessions was deemed important for engendering trust among men and enabling them to engage in modelling alternative forms of masculine behaviour which can enhance mental health and encourage greater help-seeking. The paper concludes by arguing for a relational understanding of community sport and mental health programmes, since our data indicate that by focusing on the networks of relationships involved in Offload and the social contexts in which it was to be delivered, the programme designers effectively leveraged the benefits of their collective expertise to maximise men's engagement.