Abstract Precarious labour has been on the rise globally since the 1970s and 1980s. Changing labour relations in the cleaning industry are an example of these developments. From the 1970s onwards, outsourcing changed the position of industrial cleaners fundamentally: subcontracting companies were able to reduce labour costs by recruiting mainly women and immigrants with a weak position in the labour market. For trade unions, it was hard to find a way to counteract this tendency and to organize these workers until the Justice for Janitors (J4J) campaigns, set up by the US-based Service Employees International Union (SEIU) from the late 1980s, showed that an adequate trade union response was possible. From the mid-2000s, the SEIU launched a strategy to form international coalitions outside the US. It met a favourable response in several countries. In the Netherlands, a campaign modelled on the J4J repertoire proved extraordinarily successful. In this article, transnational trade unionism in the cleaning industry based on the J4J model will be analysed with a special focus on the Dutch case. How were local labour markets and trade union actions related to the transnational connections apparent in the rise of multinational cleaning companies, the immigrant workforce, and the role of the SEIU in promoting international cooperation between unions?