In this study, the author draws on a comparison of two strikes by US healthcare workers to examine power resources and strike effectiveness. Unions mobilized a range of power resources in each case yet achieved different outcomes. The author argues that variation in bargaining power, particularly employer power resources, rather than union strategy, explains divergent strike outcomes. The author advances a relational understanding of power resources by explaining how employer resources and strategies shape labour's resources and strategies to produce outcomes for workers and their organizations.