This paper explores the process from museumization to decolonization through an examination of a Haida eagle mask currently on display in the Exploring Medicine gallery at the Science Museum in London. While elements of this discussion are well developed in some disciplines, such as Indigenous studies, anthropology and museum and heritage studies, this paper approaches the topic through the history of science, where decolonization and global perspectives are still gaining momentum. The aim therefore is to offer some opening perspectives and methods on how historians of science can use the ideas and approaches relating to decolonization in other fields, and apply them constructively to the history of science, particularly in museum settings. Decolonization is a complicated process and the focus of this paper is squarely on the preliminary steps of its implementation. To understand this process fully, the paper will recontextualize the Indigenous history of the Haida eagle mask at the Science Museum through a careful reconstruction of its provenance record. Through this process it will expose the politics of erasure and hidden voices in museum collections.