Throughout his writings, Westermarck recognises Adam Smith as the main inspiration for his theory of moral emotions. He regarded Smith as a precursor of his psychological and sociological ethics, and was thus early to highlight the descriptive and empirical nature of Smith’s moral theory. One of the main reasons for Westermarck’s appreciation of Smith’s account of the moral sentiments was that its key building blocks were compatible with Darwinian evolutionism. Although Westermarck’s conception of sympathy is much indebted to Smith, he also criticises some of Smith’s basic assumptions. Smith’s conception of the impartial spectator figures in different ways in Westermarck’s theory of morality. In Westermarck’s reading, the impartial spectator represents primarily how human beings make moral judgements on others. More specifically, Smith’s description of the gratitude and resentment people feel when they observe the actions of others from the position of a non-involved bystander helped Westermarck to formulate his theory on the nature of moral emotions. However, Westermarck simplifies Smith’s account by combining his description of two distinct species of moral approval and disapproval into a unified theory of moral emotions as retributive emotions. Smith’s impartial spectator is, for Westermarck, only secondarily about the human capacity for self-evaluation; however, the impartial spectator appears in this sense also in Westermarck’s account of self-directed moral emotions. Finally, the chapter shows that Smith and Westermarck share a similar conception of the significance of emotions in scientific inquiry.