This paper examines how Western and CEE trade unions are coping with intensifying cross-border competition. It asks what strategies they employ to increase or preserve employment levels and to improve working conditions in a transnationally competitive environment. The evidence on Polish–German trade union relations in the automotive industry suggests that labour organisations are undertaking a mix of national and cross-border initiatives, but their commitment to cross-border cooperation should not be taken for granted. The decision of Polish trade unionists to coordinate activities with their German counterparts is conditional upon the Westerners’ assistance. For German activists, transnational cooperation primarily serves the goal of limiting competition from cheaper Polish labour and is accompanied by a range of activities at national level that aim to restore competitiveness in German locations. The paper also argues, however, that the heterogeneity of social conditions in the enlarged EU increases Western European unions’ propensity to pursue cooperative solutions.