ABSTRACT Migrant workers, both regular and irregular, are at particular risk of having their rights violated. At the same time, there has been an absence of support for exploited immigrant workers from Swedish authorities and civil society. Lately, a number of trade unions and semi-union organisations in Sweden have developed methods to mobilize the rights of migrant workers experiencing exploitation on the Swedish labour market. This article investigates strategies utilized by trade unions to mobilize migrant workers’ rights by engaging with the law and the courts. It draws on qualitative interviews with trade union representatives and court judgements from the Labour Court and other civil courts. We identify legal practices that range from immediate legal assistance and everyday negotiations with employers to litigation in court. We show how the practical, aspirational, and creative engagement of a small group of trade union representatives with the law and courts has generated a new form for mobilizing the rights of migrant workers in the Swedish context. This form of legal mobilization is both instrumental and political, driven by the rhetoric of class struggle and a belief in the rights of migrant workers.