The Science Europe workshop report "Cross-border Collaboration and Portfolio Management of Research Infrastructures" builds on the Survey Report ‘Strategic Priorities, Funding and Pan-European Cooperation for Research Infrastructures in Europe" (2016) and explores the challenges facing research funding and performing organisations to design and manage balanced Research Infrastructure (RI) portfolios and design effective cross-border collaborations when setting up and running joint RIs. Discussions with a broad range of stakeholders took place at a dedicated workshop on 30 and 31 January 2017 in Dublin co-hosted by Science Foundation Ireland and the Health Research Board.