Social entrepreneurship evades easy definition and conceptualization. In this paper we attempt to advance social entrepreneurship theoretically by examining it conceptually, from a theory of the firm perspective. If social entrepreneurship entails pursuit of a double bottom line (Dees 1998), the added complexity of the social entrepreneurial venture identified by Tracey and Phillips (2007) should be discoverable from a theory of the firm perspective. Applying the knowledge-based theory of the firm to social entrepreneurship, we aver that social entrepreneurship’s added complexity is manifest when social entrepreneurs make decisions about their knowledge. In contrast to ordinary entrepreneurs, social entrepreneurs have to balance two incommensurable objectives when they form their attitude toward protection of their knowledge.