This article investigates cross-border engagement between women's organisations and other groups working on gender equality policy. It draws on interviews with activists and practitioners and two seminars—one in Belfast and one in Dublin. It is set in the context of the post-Brexit debate on the future of the island of Ireland, and the international Women, Peace and Security agenda's emphasis on the role of women and the centrality of a gender equality perspective to peacebuilding. Participants had very positive attitudes to cross-border collaboration, but in practice there was very little cross-border engagement between groups, and this lack of activity predates Brexit. The key barriers to cross-border work were perceived to be post-Brexit political turmoil, a lack of appropriate funding and a lack of knowledge of policy differences between the two jurisdictions. Participants had very little knowledge of the 'other' jurisdiction and their views were strongly shaped by historic stereotypes.