This article evaluates the changing assessments within the British trade union movement of the efficacy of European Union integration from the viewpoint of labour interests. It argues that there has been a marked further ‘Europeanisation’ of British trade unionism during the 1990s, consolidating an on-going process which previous research shows began in earnest in the mid 1980s. A shift in trade union economic policy assessments has seen the decisive abandonment of the previously dominant ‘naive’ or national Keynesianism. While there remain important differences in economic perspective between unions, these are not such as would create significant divisions over the question of European integration per se, the net benefits of which are now generally, though perhaps not universally, accepted. The absence of fundamental divisions is evident from a careful assessment of the debates about economic and monetary union at TUC Congress. The Europeanisation of British trade unionism needs to be seen within the context of an emergent regionalism, in Europe and elsewhere. It can best be understood as a rational response by an important corporate actor (albeit one whose national influence has been considerably diminished in recent decades) to globalisation and a significantly changing political economy environment.