The gist of Westermarck’s moral theory is the view that human moral judgements are based on the emotions of moral approval and disapproval. This chapter provides an overview of Westermarck’s account of the nature of these emotions, the main focus being on its psychological and social elements. The moral emotions belong to a broader class of retributive emotions, through which Westermarck locates the origins of morality in emotional reactions that are widespread among animals. Next, I look at his analysis of the characteristics by which the uniquely human moral emotions are distinguished from other retributive emotions. These distinctive features are disinterestedness, impartiality and generality. The analysis of these characteristics is part of his endeavour to identify and explore the typical social conditions in which the moral approval and disapproval arise. These concern, first, Westermarck’s examination of sympathy and other forms of emotional contagion, second, the emotional reactions of liking and disliking, and third, the connection between the moral emotions and social customs. While emphasising the emotional basis of moral judgements, Westermarck argues that these judgements reflect an interplay between emotional experiences and cognitive factors. The emotions of moral approval and disapproval also receive their moral character from the psychological phenomenon of objectification or projection, which means our tendency to interpret these emotions as the intrinsic qualities of objects and phenomena that give rise to them. I conclude by discussing Westermarck’s relation to Emile Durkheim and showing how his theory of moral emotions shows a continuous interplay between individual and social aspects of morality, which may also be called the interplay between the individual and society.