On average, immigrant workers earn less than their autochthon peers. In the literature, it is often suggested that this is due to a lesser understanding of the host country’s labour market and the possibilities to benefit from some sort of protection. This report reviews the characteristics of the immigrant workforce and analyzes the impact of unionization on the pay and benefits of immigrant workers. After controlling for systematic differences between union and non-union workers, this CEPR paper says, union representation substantially improves the pay and benefits received by immigrants.