The aim of this work is to show the philosophical principles of Agency Theory in order to understand if this theory presents an argumentation on human behavior that we can described as utilitarian, and if so, how it could be critically considered from Business Ethics. As we will see, Agency Theory is based on two main conceptual frameworks: the first one is Coase's Institutionalism as for understanding the nature of the firm and, the second one, Gary Becker's theory of economic behavior. In this paper we will show how Agency Theory incorporates Gary Becker's theory and, consequently, a description of human behavior that we can understand as utilitarian, not only when Becker ideas' have an explicit reference to the philosophical utilitarianism of Bentham and Mill, but also because of an understanding of human behavior described as individualistic and based on an evaluative maximization calculus of convenience. From Business Ethics theory, such calculus must be considered amoral and, as such, implies a culture of opportunism, among other problems within the origination.