This article draws on two Irish case studies to examine the nature and outcomes of voluntary workplace partnership (WP), and the conditions affecting its durability. We found that WP delivered mutual gains for all stakeholders at Aughinish Alumina (AAL), which were quite equally divided. While WP delivered most gains for management at Waterford Crystal (WC), and some for the union, worker gains were less. The WC partnership broke down after 10 years, but the AAL partnership continues. Voluntarist mutual gains partnership is feasible, but success and durability depends on specific clusters of contextual conditions, notably management support, a quality-focused competitive strategy, insulation from market pressures, union postures, vertically aligned bundles of mutual gains practices, institutional supports, emphasis on fairness, all party commitment to performance enhancement and capital-intensive technology. Conditions supporting WP were stronger at AAL than WC. More generally, as supports for WP in Ireland are weaker than retardants, we conclude that few mutual gains partnerships will take root, and even fewer will endure.