We report the results of a longitudinal case study depicting the relationship between internal and external legitimacy at Orion, an emergent creative professional firm. We address the following questions: How do different types of legitimacy emerge, and how do they interact to shape organizational evolution? Introducing a staged process model, we demonstrate that organizational legitimacy is a product of action, which is continually reproduced and reconstructed by members of an organization in concert with external legitimation activities. Internal and external legitimacy evolve through a process of emergence, validation, diffusion and consensus, sometimes recursively repeating the cycle when imbalances result in conflict and friction.