In this article, I describe the belief system at the centre of Mau and Dan mask spirit performances and some implications of these beliefs in practice, and I suggest an ontological framework for interpreting the ambiguous agency embodied in such performances. I ground my discussion of this ontological framework by juxtaposing ethnographic material about non-commercial, community-based mask spirit belief and practice with details of the career of an international ‘star’ mask spirit performer, Vado Diomande. I propose that the ambiguous agency at the heart of these performances is best understood using a performance framework that locates being in process. My interlocutors’ discourse about and practices of these performances suggest that, rather than looking for ontology in performance, we understand ontology as performance – or perhaps better yet, performance as ontology. Such a framework illuminates both the challenges and the strategic advantages that ontological ambiguity presents to mask spirit performers in immigrant settings in the US. This framework also provides a philosophical grounding for theories positing African art as process, and sheds light on the ways in which mask spirit performers manoeuvre in the interstices of display and disguise, addressing both belief and market demand.