The purpose of this chapter is to articulate the philosophical underpinnings of the perspective commonly known as “practice theory.” The latter originates and has grown out from the long-standing philosophical critique of the logic of scientific rationality, which underlies a large majority of theories within organization and management theory, and social science more generally. Practice theory aims to capture the basic understandings manifested in how actors and materials are entwined in a relational whole over time. Seeing actors as embedded in practices orients researchers to explore how actors follow rules and handle their experiences in enacting the practices they partake in. This chapter explores the philosophical underpinnings of practice theory, with a particular focus on Wittgenstein and Heidegger, and distinguishes three approaches to the study of practice: commonsensical theories, general theories, and domain-specific theories.