This paper investigates the ability of unions to tackle precarious work by analysing three illustrative case-studies from Denmark, Germany and the UK. It draws on the power resource theory to analyse how different dimensions of power interact with union strategies towards workers in precarious employment, shaping outcomes in both collective representation and labour market conditions. The analysis stresses how unions need multiple forms of power, with important interactions among and across different levels of power resources and important differences between countries, sectors and workplaces. The paper discusses these interactions with a specific focus on the need to develop new resources, in particular ideational resources that are inclusive to those in precarious work, and the interaction between power resources and union strategies as the availability or absence of resources affects the strategies that unions can develop.