In the 2000s an unprecedented wave of left-party victories in presidential elections swept across Latin America. Although scholars have studied variation among left regimes and how these regimes differ from neoliberal-era predecessors, few have addressed the role of labour unions and labour policy under the Left. We argue that ‘bringing unions back in’ to the analysis of left governments’ performance sharpens distinctions with neoliberal governments and unsettles existing typologies. We review the labour policies of left governments in four countries—Chile, Brazil, Uruguay, and Argentina—to show how a labour lens enriches our understanding of left governments in the region.