Private agri-food standards, along with certification and labelling schemes, are rapidly becoming the predominant mechanism by which global agricultural production and trade are governed. This article examines voluntary private social standards (VPSS) and certification schemes in agri-food system governance and contends that, while such standards may secure important localized material gains, these are not altogether unproblematic. Furthermore, the potential for voluntary social standards to confront structural injustice in the agri-food system and to contribute to a transformation towards just and sustainable agriculture and food appear rather limited. It is argued that prominent multi-stakeholder standards are increasingly prone to capture by powerful private interests, and that a central role for decisive public regulation in agri-food system sustainability should therefore not be dismissed.