The current study examines researcher–practitioner collaborations in the context of employee activism, a context in which the role of reflexivity and theorisation relate in unique ways. Specifically, we examine the collaboration between researchers and a practitioner sustainability manager, in the context of an ongoing organisational sustainability campaign at a French business school. Within the context of an ethnographic, participant observer study, we examine how the roles of “theory” and “practice” are distributed in dynamic ways, and how, across the study, roles are challenged and inverted, oscillating in dialectical moments which we term “praxis encounters”. We contribute to growing debates around academic–practitioner collaborations by showing how the roles of researchers and practitioners evolve dialectically over the course of a project, how employee activism may be studied using collaborative approaches, and how human resource managers may support employee activism. We call for future research about the variety of such dynamics across diverse contexts.