This article examines union efforts to recruit and mobilise precarious workers in a hostile environment. Formidable obstacles confront organisers’ attempts to mobilise workers to engage in collective action at workplace level in the Irish hotel sector. After an initial grassroots organising campaign, the Services Industrial Professional and Technical Union (SIPTU) adopted a public campaign as an alternative strategy to secure improvements in pay and working conditions in the sector. Our findings indicate that the union’s inability to create a sense of collective identity among workers or establish strong support for union organisation at workplace level was due to a combination of external economic factors and challenges at this level. In the absence of such support, the impact of a public union campaign is less widely felt by employers. We evaluate the extent to which this type of campaign can substitute for weak grassroots mobilisation and provide a sustainable basis for union presence in the sector.