Based on anthropological fieldwork, this article confirms that arguments about the decline of Mumbai's cosmopolitanism through the rise of regionalism and hindutva have failed to consider the idea of 'cosmopolitanism' as understood and used by local people, specifically local merchants. Reconsideration of cosmopolitanism in relation to regionalism focuses on the morality of business, as expressed by merchants in Navi Mumbai, is examined through two case scenarios. The Marathisation of signboards led by the Maharashtra Navnirman Sena (MNS) and participation in the Ganesh Festival show that their morality of business enables Navi Mumbai's merchants to adjust to various kinds of challenging phenomena, including those seen as regionalism. The same business morality, then, skillfully re-constructs the foundations of cosmopolitanism as a polyphonic folk term. © 2012 SAGE Publications.