In this chapter I argue that Adam Smith’s moral, social and economic thought was influenced by both Stoic and Epicurean sources with surprising and fruitful results. Although these schools of thought conflicted in most respects, Smith adopted and adapted elements from each to creatively construct a kind of ‘benign-realist’ social science able to explain the order of the human universe while comprehending humans as they really were rather than as we might wish them to be. By combining the Stoic idea that all of nature is both divine and benign with a pragmatic Epicurean moral psychology, Smith not only reconciles his own realist intuitions with his sincere faith in a designed universe, but produces a compelling account of how economies and societies should operate. I show this by exploring how Smith responded to the Stoic and Epicurean approaches to virtue, self-interest, benevolence, justice and our obligations to others, especially strangers and foreigners. I also explore how he applied an Epicurean sensibility to reimagine Stoic cosmopolitanism.