Ronald H. Coase and Frank H. Knight are usually considered by scholars to be the most influential and pioneering authors of the modern theory of the firm. However, it is less well known that both of them argue, in a different but often complementary way, that employment relationships and controlling authority are at the core of the nature of the capitalist firm. In this paper, after considering the particular circumstances of the period of the 1920–1940s, we show the close relation between Coase and Knight and analyse the theoretical elements that both connect and distinguish these two main authors from the “Chicago School”.