The chapter opens with a short passage that bridges from the time period covered by the previous chapters in this section, twelfth to early seventeenth centuries, to the period considered here, the twentieth century. Between the seventeenth and nineteenth centuries, the relation between business/economics and ethics fundamentally weakens, so that the way Thomist thinkers deal with questions in these fields in the twentieth century is often more fragmented than in the past. Similarly, economists and business experts themselves rarely make reference to philosophical ethics and almost never to Thomism. On the other hand, Thomism receives a major boost at the end of the nineteenth century, thanks to Pope Leo XIII, who also launches what becomes a new body of thought known as Catholic social teaching (CST), and thus, CST is much influenced by Thomism, although on some key points of importance to business ethics, there has been some divergence between Thomism and CST. Three areas of some divergence are discussed here. Key concepts within the Thomist/CST body of thought that are of importance for business ethics include the concept of what is good, the nature and dignity of the human person, the common good, and human virtue. Since the financial crisis, in connection with the revival of virtue ethics, Thomism is being more discussed, although the main source for these discussions is usually Aristotle or MacIntyre; after these two, however, CST does also sometimes figure. Where Thomism is discussed directly, it is increasingly so as to provide a general frame for business ethics, especially in global and culturally diverse contexts. Some book-length treatments of Thomism/CST and economics and business are discussed, with a focus on the last great work of Arthur Fridolin Utz on economic ethics, along with the specific areas of business ethics where Thomistic thought has been influential. An assessment of the influence on business ethics of Thomism and CST is made. Thanks to the rising interest in virtue ethics for business, mainstream business ethics is taking Thomism and CST more into account, and the kinds of problems that business must increasingly face, combined with what Thomism and CST can offer to remedy these problems, leave open the potential for a “breakthrough” in the not-too-distant future.