In this contribution I engage with the question of the end of theory from a poststructuralist perspective. I begin by revisiting the making of International Relations as a discrete theoretical endeavour from Waltz (1979) to Wendt (1999), around, respectively, the efforts to unearth the structures of international politics that carved out the international as a distinct site of political analysis, and the appraisal of these structures as social structures (Wendt, 1999). I then revisit the origins of poststructuralism via the works of Jacques Derrida and Judith Butler, in order to bring its founding moves to bear directly on International Relations constructivism. Engaging with constructivism’s founding fathers, Nicholas Onuf, Alexander Wendt and Friedrich Kratochwil, I show that the search for unconstructed universals, grounded in an innate ‘human nature’, persistently haunts International Relations constructivism, even when it foregrounds language as the medium of social construction, and notably when it engages the question of gender. Just as language provided the original site for orchestrating the ‘moving beyond’ (the ‘post’ of poststructuralism) fixed, naturalized structures, I argue that a return to language holds the promise of renewal, and of constructivism’s being able to fulfil its founding promise to theorize constitutivity and the constructed-ness of International Relations’ world.