Despite its central position in the history of European and Christian thought on the protection of human dignity, the virtue of mercy is currently a problematic and under-developed concept in business ethics, compared to related ideas of care, compassion or philanthropy. The aim of this article is to argue for its revival as a core principle of ethical business practice. The article is conceptual in method. An overview is provided of the scope of contemporary business ethics research on related topics and clarifies some of the similarities and differences between mercy and popular terms, such as compassion and prosocial behaviour. The question is then explored as to why mercy has so little traction in business ethics. Some of the history of the idea of mercy in European and Anglophone philosophy is discussed, from Anselm and Aquinas to the present day, showing how discourse on mercy came to be split into a wider concept of the prevention and alleviation of suffering (misericordia) and a narrower one of clemency or leniency. Aquinas’s wide concept of the virtue of misericordia is developed as the basis for a principle of mercy, which is applicable directly to corporations. The practical implications of this for standards of corporate behaviour towards employees and other stakeholders are then considered through the introduction of a ‘vulnerability grid’. The grid offers a critical contrast to other analysis tools, such as stakeholder power-interest matrices. Cases drawn from empirical studies are used to illustrate application of the grid and to challenge some common assumptions of stakeholder theory.