This chapter provides an overview of the attitude of trade unions in the UK towards shareholder engagement and outlines the activity undertaken by the Trades Union Congress (TUC) to promote responsible investment. The chapter explains the 'workers' capital' perspective on investment as it has been articulated by trade unions internationally. It also describes the TUC's specific work in this area such as organising pension fund trustees and surveying fund managers on how they exercise clients' shareholder voting rights. The chapter concludes with a discussion of the development of responsible investment in the UK, some of the challenges it has faced and the role of the labour movement in promoting responsible investment in the future.