This article aims to reflect on the aporias and paradoxes of a postcolonial, collaborative research approach to ethnographic collections dating from colonial times. While, at least in Germany, ‘provenance research’ and ‘collaboration’ have become politically opportune, important questions concerning the possibilities or impossibilities of overcoming colonial categories, epistemologies and imbalances of power remain to be answered. Based on research and collaboration with stakeholders over the course of two projects on the Tanzania collections of the Ethnologisches Museum Berlin, this article asks how far ‘collaboration’ and ‘decolonization’ risk remaining merely empty, fashionable phrases, if, on the one hand, today’s concern with the colonial context of collections in European museums seems to be to a great extent self-referential and avoiding radical criticism of today’s power asymmetries; and, on the other, the deconstruction of colonial class, gender, race, and ethnic categorizations, and of the resulting representations is hindered – if not made impossible – by the epistemologies implicit in the order of the collections themselves but also by identity politics