We examine the roles of episodic and systemic forms of power in radical organizational change. Drawing on a study of three attempted transformations in professional service firms from traditional professional partnerships into managed professional businesses – one relatively complete and two incomplete – we identify two key mechanisms that link episodic and systemic forms of power and show how those mechanisms affect the likelihood that organizations will be able to successfully undergo radical change. We find that episodic power is able to initiate and energize radical change when it represents a significant break from traditional authority structures and is legitimated through appeals to traditional organizational values. We find that systemic power is able to institutionalize radical change when the systems associated with it are legitimated by the skilled use of language by key actors and then left to operate independently by those actors. By articulating the specific mechanisms that link episodic and systemic power, our study provides a more complete model of the role of power in radical change, enabling better prediction of the likelihood of successful transformation and a fuller theoretical explanation of change outcomes.