The Convention on Biological Diversity (CBD) continues to promote marine protected areas (MPAs) as a preferred tool for marine biodiversity conservation, in spite of concerns over their effectiveness and equity. However, explanations for this consensus on the utility of MPAs focus primarily on their measurability and ignore the ways in which they are conceptualized through ongoing governance processes. Drawing on the results of collaborative event ethnography at the Tenth Conference of the Parties to the CBD, this paper adopts the concepts of boundary objects and scalar narratives to analyze the ways in which consensus on MPAs is produced, in spite of conflicting understandings of MPA forms and functions. Both a local narrative of participatory MPAs and a global narrative of science driven high seas conservation articulate a regional scale as ideal for MPA governance, although with different priorities. Ultimately, consensus at the CBD is enabled only by accommodating competing visions of MPAs.